News | Nov. 19, 2020

More Afraid of Your Friends Than the Enemy: Coalition Dynamics in the Korean War, 1950–1951

Joint Force Quarterly 99

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Fideleon O. Damian is a Military Analyst working in the Washington, DC, metropolitan area.

United Nations forces withdraw from North Korean capital, Pyongyang, recrossing 38th parallel, ca. 1950
United Nations forces withdraw from North Korean capital, Pyongyang, recrossing 38th parallel, ca. 1950 (U.S. Information Agency/U.S. National Archives and Records Administration)
United Nations forces withdraw from North Korean capital, Pyongyang, recrossing 38th parallel, ca. 1950
United Nations forces withdraw from North Korean capital, Pyongyang, recrossing 38th parallel, ca. 1950
United Nations forces withdraw from North Korean capital, Pyongyang, recrossing 38th parallel, ca. 1950 (U.S. Information Agency/U.S. National Archives and Records Administration)
Photo By: U.S. Information Agency/U.S. National Archives and Records Administration
VIRIN: 201113-D-BD104-018

Collaboration with other countries is an integral part of the U.S. National Security Strategy. Its most recent version notes that “allies and partners are a great strength of the United States” that “add directly to U.S. political, economic, military, intelligence, and other capabilities.”1 Since the end of the Cold War, countries have preferred to collaborate through coalitions rather than formal alliances because the latter are more liable to impose political constraints. Coalitions, according to Patricia Weitsman, are “ad hoc multinational undertakings that are forged to undertake a specific mission and dissolve once that mission is complete.”2 Weitsman claims that coalitions tend to be more cohesive than formal military alliances because of their ad hoc nature, the ability of the coalition leader to tailor membership to suit the mission, and, most relevant to this article, the absence of formal institutions and consultative processes found in formal alliances.3 This viewpoint suggests that coalition members do not need to prepare for cases where strategic divergences occur or to develop mechanisms to manage a member’s internal dynamics.

This article argues that military and civilian leaders should recognize the potential for strategic divergences between coalition partners and be ready to manage them; it uses as a case study the relationship between the United States and its primary Western coalition partner, the United Kingdom (UK), during the Korean War. The United States and the UK joined the United Nations (UN) coalition during the summer of 1950 with their interests initially aligned around a common goal: the defense of South Korea from communist aggression. By the end of 1950, however, the UK concluded that U.S. actions that could intentionally or unintentionally escalate or broaden the conflict posed a more imminent threat than communist military operations.4 In response, the UK acted to prevent any U.S. operational or diplomatic initiatives that the British judged as harmful to their national aims. Throughout the winter of 1950 to 1951 and the following spring, to maintain coalition cohesion, the United States had to reassure its partner that it would prosecute the conflict within military and diplomatic parameters acceptable to the British.

Given the importance of international partnerships to U.S. security strategy, policymakers and scholars should look to the past for lessons on how to form and run coalitions. Studies of coalition dynamics often gravitate toward models of success rather than failure for their insights. Of the prior century, the two most prominent successes often cited as models to emulate are the Allied coalition to defeat Germany and Japan in World War II and the U.S.-led coalition to expel Iraq from Kuwait in the Gulf War.5 In both cases, the outcomes were unqualified successes, and the coalition members managed to maintain general alignment at least until the coalition achieved its military goals. However, cases that produced more ambiguous results and internal tensions over the conduct and direction of the conflict, such as the Korean War, merit equal attention for the insights they can provide in today’s more complex strategic environment.

Between 1951 and 1953, the United States and the UK fought as part of a UN coalition to prevent a communist takeover of the entire Korean Peninsula. The war began with Soviet-sponsored North Korea invading south of the 38th parallel in June 1950 and nearly succeeding in conquering the whole of South Korea save a small enclave near Pusan. A UN counterattack in September 1950 shattered the North Korean military’s fighting capabilities and liberated all the territory lost the previous summer. The UN decision to advance north of the 38th parallel, however, prompted China to intervene on North Korea’s behalf and raised fears that UN forces would evacuate the peninsula. By spring 1951, UN forces had recovered sufficiently, and the conflict settled into a protracted war of attrition that ended after 2 years of negotiations produced, in July 1953, an armistice that restored the status quo antebellum.

Korea itself was a largely peripheral strategic issue to both the United States and the UK in summer 1950, and both nations joined the UN coalition less concerned with the outcome on the peninsula itself than with its implications for Anglo-American global cooperation and the opportunity to advance their national ambitions. For the UK, Asia ranked lower than continental Europe in national priorities; within Asia, the survival of South Korea ranked below continued control over its two imperial colonies, Hong Kong and Malaya. Similarly, for the United States, Asia ranked lower than Europe, and South Korea ranked lower than the security of Japan, Taiwan, and the Philippines in the region. Kim Il-sung’s invasion and the possible reunification of the peninsula under the communist banner, however, transformed Korea from a peripheral issue into a Cold War litmus test of Western resolve and solidarity.6

The United States and the UK viewed Korea as a bellwether for Anglo-American cohesion on more critical issues at the beginning of the war. Both nations assessed that Korea would test the credibility of its commitment to anticommunism. Each government judged that the failure to counter communist aggression in Asia would encourage even bolder activity by the Soviet Union elsewhere. The United States and the UK also recognized that although Korea was a peripheral global interest, the absence of a coordinated response would serve as an unfortunate omen for future cooperation on higher stakes issues. The two nations considered the Korean crisis a test of the principle of collective security and the legitimacy of the newly established UN as the guarantor of the post–World War II order. Lastly, neither nation wanted a war in Korea to expand into a broader conflict with China or the Soviet Union.7

Anglo-American cooperation in Korea was based as much on self-interest as it was on shared interests. The Americans wanted additional partners in the coalition in order to reduce the demands on their military resources. British participation also strengthened the U.S. message that the intervention was an internationally sanctioned response to a threat to global stability, providing the Harry S. Truman administration with domestic and international political legitimacy. The British expected that their support in Korea would prompt the Americans to reciprocate with a stronger commitment to the defense of Western Europe. The British also calculated that despite unquestionable U.S. military and economic superiority, participation would build political capital and goodwill that they could use to steer the Americans to act responsibly and in ways that did not jeopardize British interests.8

On paper, though, the British appeared unlikely to challenge U.S. coalition leadership against the balance of overwhelming U.S. political and military power and shared objectives. For example, the United States supplied an entire field army of several hundred thousand men—compared with the two UK brigades of less than 10,000 men total who depended on U.S. logistics and supply assistance.9 Outside of Korea, the UK also needed U.S. assistance to advance its nuclear weapons research, to rebuild its shattered economy, and to defend the European continent against potential Soviet aggression.10

The British did have reservations about aligning themselves too closely with the Americans, but those concerns were secondary in the British strategic calculus until the Chinese intervention. As much as the UK valued the Anglo-American relationship and its access to U.S. military and economic support, the British were equally uncertain whether U.S. leadership would prevent a third world war or instigate it. Differences over the legitimacy of the Chinese communist government was another area of departure that would have consequences for Anglo-American relations as the war progressed. The United States still considered Chiang Kai-shek’s nationalists in Taiwan the legitimate government of China; however, the UK, in order to maintain its economic interests in China and its control over Hong Kong, recognized Mao Zedong’s government in January 1950.11 Once the Chinese entered the conflict, the British feared that Mao would move against their Asian interests, and such concerns likely contributed to the resistance to provoking him directly.

Men and equipment parachute to ground in operation conducted by United Nations airborne units, ca. 1951
Men and equipment parachute to ground in operation conducted by United Nations airborne units, ca. 1951 (DOD/U.S. Information Agency/U.S. National Archives and Records Administration)
Men and equipment parachute to ground in operation conducted by United Nations airborne units, ca. 1951
Men and equipment parachute to ground in operation conducted by United Nations airborne units, ca. 1951
Men and equipment parachute to ground in operation conducted by United Nations airborne units, ca. 1951 (DOD/U.S. Information Agency/U.S. National Archives and Records Administration)
Photo By: DOD/U.S. Information Agency/U.S. National Archives and Records Administration
VIRIN: 201113-D-BD104-014

Chinese Intervention Catalyzes a Strategic Rift

The Chinese counterattack in the winter of 1950–1951 shattered UN hopes of an imminent victory and triggered the British loss of confidence in U.S. leadership, which prompted the UK to act to protect its strategic interests. After the entire Korean Peninsula was nearly lost in summer 1950, a successful UN counterattack—combining an amphibious assault at Inchon with an Eighth Army breakout from the Pusan perimeter that September—broke the North Korean military’s back. Buoyed by this drastic reversal of fortune and seeing an opportunity to roll back communism, President Truman secured UN approval to expand the conflict beyond the defense of South Korea. The new aim was to reunite the peninsula under the aegis of a U.S.-sponsored government instead of merely containing the spread of communism.

Beginning in October 1950, Chinese “volunteers” entered Korea to prevent the consolidation of the peninsula under a U.S.-backed government.12 Although the first skirmishes occurred in late October, the most serious blows fell on November 27, when a Chinese counterattack caught complacent UN forces off guard and sparked a panicked retreat south. The next day, General Douglas MacArthur announced that he faced an “entirely new war” with the entry of more than 200,000 Chinese troops.13 By mid-January 1951, UN forces had retreated across the 38th parallel and abandoned Seoul, undoing much of the previous autumn’s gains.

The UN military position stabilized after a change of command in the Eighth Army and the loss of momentum in the Chinese offensive due to overtaxed logistics.14 After assuming command of the Eighth Army following Lieutenant General Walton Walker’s death in an accident, Lieutenant General Matthew Ridgway replaced ineffective unit commanders and restored troop morale, enabling the UN coalition to steady its battlefield positions. By mid-January, it was clear that the Chinese were having difficulty sustaining their advance after weeks of combat and needed time to reorganize their personnel and logistics. By late January, UN forces had sufficiently recovered under Ridgway, launching offensives that would eventually retake Seoul and return UN positions to the 38th parallel.

The UK Fears the United States More than China

Despite the improved military situation by February 1951, the British ceased showing Washington deference and began taking action to protect their national interests; they had lost confidence that the Truman administration would not expand the conflict.15 Five factors contributed to this strategic divergence:

  • the lack of preparation by the UN coalition for drastic changes to the strategic environment
  • UN Supreme Commander MacArthur’s influence in decisionmaking
  • the minimal weight given to British input into coalition decisionmaking
  • the U.S. domestic political environment
  • British perceptions that Washington was vulnerable to strategic mistakes.

The British feared that these factors would lead to a miscalculation that would draw the coalition into a direct war against the Chinese and possibly a more openly and directly involved Soviet Union.

The UN coalition’s collective inability to anticipate a Chinese intervention or prepare responses probably played no small part in British fears that additional miscalculations were in play. Although Truman and his senior advisors had raised the possibility that the Chinese could enter the conflict if UN forces pressed beyond the 38th parallel, MacArthur assured them that a large-scale intervention was unlikely.16 Neither back-channel communications from Mao’s government nor U.S. intelligence assessments warning of a possible Chinese intervention was deemed of sufficient specificity to challenge the field consensus that the People’s Republic of China would not respond with a significant military action.17 London had passed on to Washington warnings, received through New Delhi as early as September 27, that the Chinese would enter the conflict if the United States crossed the 38th parallel.18 It appears, however, that up until the Chinese intervened in force in November, London and Washington were uncertain whether it would occur.19 While Washington and London agreed an intervention would risk escalating the war, the focus of discussion was how to dissuade the Chinese from entering it.20 The two governments also do not appear to have substantively discussed how the coalition would deal with the fallout of Chinese actions or the implications for the coalition itself.

Another factor behind London’s loss of confidence was its discomfort about MacArthur’s influence over decisions and its uncertainty of whether Truman or MacArthur was dictating Washington’s Korea policy and strategy. The British probably feared that the Truman administration’s inability to control the general left the door open for MacArthur or his allies to force an escalation. Following a meeting with Secretary of State Dean Acheson in mid-November, British ambassador Oliver Franks assessed that internally the Secretary of State lacked the power or will to convince the Joint Chiefs of Staff (JCS) to pay less deference to MacArthur’s decisionmaking.21 In a November 22 telegraph, British foreign secretary Ernest Bevin told Franks that the British House of Commons was concerned that MacArthur’s actions could produce a general war with China.22 Further contributing to London’s lack of confidence, Acheson told Bevin on November 24 that a British proposal to the UN establishing a demilitarized zone in North Korea would hurt the morale of UN forces and that it was important all UN members show every possible support to the troops.23

The British also assessed that the Chinese intervention resulted from Washington not paying sufficient attention to British perspectives and concerns in their decisions, despite British military contributions to the coalition. Air Chief Marshal Sir William Elliot, the chief staff officer to the Ministry of Defence, informed Prime Minister Clement Atlee after the November 20 meeting that the British chiefs of staff had concluded it was necessary to start presenting their views to the Americans in the “most forcible and unequivocal terms.”24 In his November 22 telegraph to Franks, Bevin informed him that as foreign secretary, he was placed in an awkward situation because British troops fought under UN authority, but London had little say in how the UN commander would use those troops. Bevin assessed that the UK needed to press the United States to consult more with those UN member states supplying forces for the war.25

British assessment of U.S. domestic politics further reinforced doubts the Truman administration could keep the war limited. During a November 20 meeting of the British chiefs of staff committee, William Slim, chief of the Imperial General Staff, expressed his concerns that internal U.S. politics were undercutting the Truman administration’s ability to contain the scope of the conflict and exercise greater control over MacArthur’s operations.26 By November 25, the British chiefs of staff told Arthur Tedder, the head of the British Joint Services Mission in Washington, that the U.S. domestic climate made it difficult for British diplomats to moderate American behaviors, despite a shared interest in preventing an expansion.27

Washington’s public messaging probably further raised London’s concerns that its coalition leader could make a strategic miscalculation under pressure. During a press conference on November 30, Truman made statements that especially troubled the British and other allies. First, he stated, “We will take whatever steps are necessary to meet the military situation, just as we always have.”28 A follow-on question asked whether this included the use of the atomic bomb, to which Truman replied, “There has always been active consideration of its use.” Truman went even further when he stated that the decision to employ atomic weapons rested with the field commander. Although this was certainly not his administration’s policy and Truman subsequently clarified his statements, many in the international community interpreted them as a threat to escalate and use the bomb.29 The haste with which Truman spoke and then backtracked his statements probably did little to reassure British decisionmakers that they could unconditionally rely on Washington to have the internal clarity and prudence to make sound strategic decisions.

General of the Army Douglas MacArthur inspects troops of 24th Infantry on his arrival at Kimpo Airfield
General of the Army Douglas MacArthur inspects troops of 24th Infantry on his arrival at Kimpo Airfield for tour of battlefront, February 21, 1951 (U.S. Information Agency/U.S. National Archives and Records Administration)
General of the Army Douglas MacArthur inspects troops of 24th Infantry on his arrival at Kimpo Airfield
General of the Army Douglas MacArthur inspects troops of 24th Infantry on his arrival at Kimpo Airfield
General of the Army Douglas MacArthur inspects troops of 24th Infantry on his arrival at Kimpo Airfield for tour of battlefront, February 21, 1951 (U.S. Information Agency/U.S. National Archives and Records Administration)
Photo By: U.S. Information Agency/U.S. National Archives and Records Administration
VIRIN: 201113-D-BD104-016

The Consequences of Strategic Divergence: Preventing a Wider War

It was clear that by late November, the UK had lost confidence that the United States could keep the war limited and would not escalate by design or accident. The UK had also lost confidence that its strategic interests were safe. The fear and uncertainty created by the American response to the Chinese intervention was the final straw that prompted the UK and other allies to move to protect their national interests against any U.S. actions that had the potential to escalate the war.30 Truman’s press conference on November 30, 1950, especially catalyzed the British to take more active and direct measures. From December 1950 to May 1951, as long as the British feared that their coalition leader could control the situation, the UK exercised what influence it could to prevent the United States from expanding the war. More important, British fears had risen to the point that the UK was willing to risk damage to Anglo-American relations by publicly breaking with the United States in the UN.

Between December 1950 and May 1951, the UK took action to counter or delay potential American actions, two in the military sphere and one in the political, that could harm its strategic interests. First, the British worried that the United States would employ atomic weapons. Second, the Atlee government feared that the Truman administration would succumb to MacArthur’s demands to bomb Manchuria. Finally, London was concerned that the United States could push for punitive UN resolutions against China. The British concluded that by engaging with the United States to force it to address their concerns, they could at least stall—and, if necessary, block—the United States from taking actions that London viewed as damaging. From the British perspective, these actions would compel the Americans to consider an alternative view of the risks they were taking and the possible unintended consequences.

The British leveraged the Truman-Atlee meetings of December 3–8, 1950, to voice concerns over the use of atomic weapons and to enhance British prestige in the relationship.31 Although the United States had no immediate intentions to employ the atomic bomb at the time of Atlee’s visit, Truman’s November 30 statements had made it necessary for the UK to seek assurances on U.S. intentions regarding atomic weapons. The minimum American concession Atlee hoped for, initially, was Truman’s commitment that any use of atomic weapons would involve consultations with the British government. After being informed of the domestic unfeasibility of such a proposal by Acheson, Atlee was satisfied with a public commitment by Truman that expressed his hope that circumstances would “never call for the use” of atomic weapons. Truman also promised he would “keep the Prime Minister at all times informed of developments which might bring about a change in the situation.”32

While the Truman-Atlee conference seemed to assuage immediate concerns over atomic weapons, the British still feared they would find themselves in a broader war if the United States expanded the air conflict into Manchuria. Of particular concern to the British were U.S. proposals to give the UN commander permission to conduct “hot pursuit” of communist aircraft attacking UN troops over the Yalu River and into Manchuria. MacArthur was still the UN commander when the British rejected an additional U.S. proposal on April 6, 1951, to allow retaliatory bombings of airbases in Manchuria that were the origin of Chinese air attacks. London requested that Washington instead first consult its allies and issue a warning to the Chinese to cease air attacks before crossing into Manchuria.33 The British assessed that giving MacArthur the authority to conduct either kind of air action risked widening the war.34 Even after MacArthur’s removal later that month, the British refused to accept American proposals unconditionally and insisted on having some input out of fear that Truman could authorize a drastic action in response to domestic pressure. Although the Pentagon would later give MacArthur’s replacement, Ridgway, authority to conduct retaliatory air attacks, the instructions the JCS issued acknowledged allied sensitivities. Ridgway had to consult with the JCS before authorizing any strikes; if this was not feasible, he was to inform the JCS as soon as possible and avoid discussing the matter publicly until Washington had notified its allies. By insisting any decisions regarding airstrikes in Manchuria involve other coalition partners, the British had gained some additional ability to influence and prevent a hasty action that could drag them into a wider war.

Equally concerning to the British was an American demand for a UN resolution to condemn China as an aggressor and impose punitive sanctions. Passage of such a resolution risked hardening Chinese resolve and undercutting efforts by the British and others to negotiate a ceasefire.35 The British became aware of the U.S. intent to call for a UN resolution condemning China at the end of December 1950 after the State Department began soliciting support from member states for the measure. Working together with Canada, the UK started building support within the UN and with its Commonwealth to delay passage of such a resolution.36 First, the British delayed the resolution’s proposal until January 20 by convincing the United States to allow China to accept a UN statement of principles for a ceasefire first.37 Next, the British stalled passage of the U.S.-backed UN resolution by objecting to language that implied authorization for economic sanctions against China, which the British feared would only provoke the Chinese. The British were sufficiently concerned about the resolution that they were willing to publicly break with the United States and vote against its passage unless the United States addressed their concerns.38 Recognizing that a public “no” vote by the British could prompt a domestic political backlash and undermine U.S. congressional support for the more strategically important rearmament of Europe, the Truman administration amended the resolution with additional language to assure the British that any proposed sanctions against China would be brought to the UN first.39

The most important outcome of British actions was that London was able to protect national interests by diminishing the possibility that the United States could unilaterally escalate the conflict. While some scholars have argued that British efforts had minimal influence on U.S. decisionmaking or consequences regarding China, these claims do not give the British sufficient credit in reducing the prospects of a U.S. miscalculation. For example, Callum MacDonald has argued that the United States had no intention of expanding the war and that the UK would have had little capability to prevent the United States from doing so even if it had.40 Although Peter Lowe has argued that British fears were valid and the winter of 1950–1951 was the closest the United States ever came to using atomic weapons in Korea, he also claims that British dependency on the Americans hindered UK capacity for independent action.41 William Stueck, however, contends British and UN members did reduce the chances of expanding the war because they sufficiently delayed the United States from a hasty overreaction and created the space and time for the military situation to stabilize. These improved battlefield conditions reduced the pressure on Truman to authorize a drastic action to salvage the U.S. position.42 Though British actions alone were not decisive in ensuring the Korean War did not escalate further, they did make it more difficult for the more powerful ally to drag the UK into a broader conflict unintentionally and without at least considering the ramifications of such actions.

Another important consequence of the UK actions was that U.S. political and military strategic decisionmaking in the war became less unilateral and paid more attention to internal coalition strategic concerns to maintain cohesion. According to Stueck, after the winter of 1950–1951, the Truman administration probably lost the latitude to employ measures that could have forced the communists to agree to an armistice earlier, because of the Atlee government’s resistance.43 Although using atomic weapons, bombing Manchuria, or other militarily expedient actions could have changed the military balance, the British by their actions made it clear the United States would have to risk paying a high political cost if the Truman administration acted unilaterally and without deliberation. If the United States was willing to go beyond what its allies deemed prudent, it would have to consider whether the action merited a public break with its partners that would undermine U.S. claims that it was acting in Korea to defend the international order.

President Harry S. Truman, Secretary of State Dean Acheson, Secretary of Defense George C. Marshall, and Prime Minister Clement Attlee, at the White House, Washington, DC, December 6, 1950
Clockwise from lower left, President Harry S. Truman, Secretary of State Dean Acheson, Secretary of Defense George C. Marshall, and Prime Minister Clement Attlee, at the White House, Washington, DC, December 6, 1950, autographed by President Truman (Courtesy Harry S. Truman Library & Museum/National Park Service/Abbie Rowe)
President Harry S. Truman, Secretary of State Dean Acheson, Secretary of Defense George C. Marshall, and Prime Minister Clement Attlee, at the White House, Washington, DC, December 6, 1950
President Harry S. Truman, Secretary of State Dean Acheson, Secretary of Defense George C. Marshall, and Prime Minister Clement Attlee, at the White House, Washington, DC, December 6, 1950
Clockwise from lower left, President Harry S. Truman, Secretary of State Dean Acheson, Secretary of Defense George C. Marshall, and Prime Minister Clement Attlee, at the White House, Washington, DC, December 6, 1950, autographed by President Truman (Courtesy Harry S. Truman Library & Museum/National Park Service/Abbie Rowe)
Photo By: Courtesy Harry S. Truman Library & Museum/National Park Service/Abbie Rowe
VIRIN: 201113-D-BD104-074


Although they occurred nearly seven decades ago, the tensions in the U.S.-UK coalition during the winter of 1950–1951 offer several salient lessons on what future warfighters and policymakers should consider when attempting to mitigate strategic divergences among coalition members. It is impossible to prevent all friction; however, devoting more time and attention to managing coalition relationships in strategy formation and execution could reduce the risk of members working at cross-purposes during periods of acute crisis. These lessons are equally valid for ad hoc groupings assembled for a specific objective and permanent formalized alliances.

Embrace the Complexity of Coalitions to Manage Them Better. Quantifiable aspects such as money, troops, and weapons platforms provide readily identifiable metrics to understand relative importance within a coalition and the advantages gained from being in one; however, policymakers and planners must appreciate the complex nature of coalitions to manage them effectively. As the Korean War example illustrates, the influence and importance of a coalition member are not gauged in quantifiable, proportionate, or direct terms. Current strategic leaders should recognize that quantifiable factors mask other dynamics that carry with them outsize benefits and costs. When working with a coalition partner, choices should be made based on the strategic value of the relationship, of which military forces are only one dimension. Both parties in the Anglo-American relationship recognized the value of the British participation as being more than just men and materiel, and this meant the consequences of failed cooperation in Korea would extend into immediate and longer term strategic matters. Without this recognition, the American imperative to address British concerns might not have emerged.

Interagency Cooperation Will Be Crucial to Managing Complexity. A coalition is as much a diplomatic relationship as it is a military one—and needs strategic leaders who are comfortable operating in both realms. Warfighters will need to pay as much attention to diplomatic initiatives as they do to military operations in the field (and vice versa for diplomats). Furthermore, proper management of this complexity will likely require coordination across the spectrum of government to ensure all activities complement each other. Effective strategic leadership will require leaders who are educated in thinking broadly about issues and capable of working across government agencies.

Address Partner Concerns over Politically Driven Changes to Coalition Dynamics. Military and civilian strategic decisionmakers alike should recognize that coalition partners pay attention to domestic politics and need to be reassured once differences emerge. Planners and policymakers must be ready to take preemptive actions to assuage and reassure coalition partners when domestic trends seen as harmful for the coalition’s cohesion and partners’ interests emerge. The British astutely observed that a U.S. President’s ability to control policy had limits and that, with sufficient public outcry, political opponents in Congress or military leaders such as MacArthur could compel Truman to take measures he did not want to employ or in haste. If political forces of a coalition partner are driving events in a direction that could affect the broader coalition, then that coalition member should do what it can to include partners in shaping a collective response.

Coalitions Should Have Contingency Plans and Processes to Deal with Major Recognized Potential Strategic Shifts. Much of the tension between the United States and the UK emerged because of the sudden strategic shock of China’s entry into the war. Although it is impossible to predict everything that could happen in war, both the United States and the UK considered the possibility of Chinese intervention and recognized it would have significant strategic implications. Despite such mutual concern, apparently no in-depth discussion took place on what Chinese intervention would mean for the broader coalition or how it would respond. When a coalition member raises a possible strategic development of concern, the prospects and the implications should be deliberated with some rigor. In their strategic planning, coalitions should at least have mechanisms in place to consider the conditions under which these developments could occur, how such an event would influence their participation, and what modifications to overall strategy and operations members would accept.

Coalitions Members Should Work to Reinforce Harmony, Even Among Historical Partners—Absent Effort, Relationships Risk Decaying. Dominant members of a coalition should not take for granted that past goodwill will persist indefinitely. When deciding how much to consult with coalition partners, prudence dictates erring on the side of more consultation, reassurance, and engagement. When circumstances require rapid responses that prevent extensive deliberations, the preexisting trust and goodwill built by earlier engagements become all the more vital in providing reassurance that members will act responsibly and to the coalition’s benefit. Despite a recent history of close collaboration, close cultural ties, and close personal ties among senior leaders, disagreements and tensions still developed between the Americans and British. Both the United States and the UK had domestic political considerations and their national interests to factor into their respective strategic calculus, and when one party perceived the two were falling out of alignment, it acted to protect those interests. While the United States did wield tremendous political and economic levers to influence behavior, it is essential not to underestimate the effects of constant engagement across all levels of government in easing British fears.


Although the United States is unlikely to experience an imminent, direct military challenge to its hyperpower status, cooperation with other friendly nations in U.S.-led coalitions will be vital to our ability to respond when that moment arrives. What this study has shown is that even disproportionately powerful nations can face challenges to their leadership and limitations to their ability to act unilaterally when their actions pose a risk to their partners. Cases such as Korea could be useful for anticipating the security challenges that lie ahead because the volatility, uncertainty, complexity, and ambiguity that shaped Anglo-American relations seven decades ago will continue to define the strategic environment. Furthermore, future conflicts will almost certainly involve the United States working with multiple coalition partners, who in some cases will have longstanding histories of mutual antagonism and mistrust of one other.

Leading coalitions will place heavy burdens on the United States, but the current reality is that it cannot meet the looming challenges of transnational threats, regional upstart regimes, and revisionist peer/near-peer challengers alone. Prudence dictates that rather than waiting until the actual crisis occurs, future leaders should begin preparing and asking difficult questions now about how we can better manage our coalitions against these threats. History shows us that a better understanding of the nature of the challenges that lie ahead is essential to being prepared to deal with them when the time comes. Moreover, as this article has shown, looking at cases of friction and difficulty between partners can provide insights that just looking at unambiguous strategic successes cannot. Further study into other such cases could help better inform our ability to anticipate and manage these challenges. JFQ


1 National Security Strategy of the United States of America (Washington, DC: The White House, December 2017), 37.

2 Patricia A. Weitsman, “Wartime Alliances Versus Coalition Warfare: How Institutional Structure Matters in the Multilateral Prosecution of Wars,” Strategic Studies Quarterly 4, no. 2 (Summer 2010).

3 Ibid.

4 Thomas Hennessey, Britain’s Korean War: Cold War Diplomacy, Strategy, and Security, 195053 (Manchester: Manchester University Press, 2015), 3–4, 108–166; William Stueck, The Korean War: An International History (Princeton: Princeton University Press, 1995), 127–157, 330–347.

5 For examples, see Mark A. Stoler, “The Grand Alliance in World War II,” and Richard Swain, “The Gulf War, 1990–1991: A Coalition of Convenience in a Changing World,” in Grand Strategy and Military Alliances, ed. Peter R. Mansoor and Williamson Murray (Cambridge: Cambridge University Press, 2016), 136–165, 343, 375.

6 Dean Acheson, The Korean War (New York: Norton, 1971), 16–34; Anthony Farrar-Hockley, The British Part in the Korean War, vol. 1: A Distant Obligation (London: Her Majesty’s Stationery Office, 1991), 1–33, 83–105; Hennessey, Britain’s Korean War, 17–44, 331–348; Harry S. Truman, Memoirs, vol. 2 (Garden City, NY: Doubleday and Company, 1956).

7 Acheson, The Korean War, 16–34; Farrar-Hockley, The British Part in the Korean War, vol. 1, 1–33, 83–105; Hennessey, Britain’s Korean War, 17–44, 331–348.

8 Acheson, The Korean War, 16–34; Farrar-Hockley, The British Part in the Korean War, vol. 2, 1–44, 83–105; Truman, Memoirs, vol. 1, 331–348.

9 Jeffrey Grey, The Commonwealth Armies and the Korean War: An Alliance Study (Manchester: Manchester University Press, 1990), 167–181.

10 Farrar-Hockley, The British Part in the Korean War, 1–33, 83–105.

11 Hennessey, Britain’s Korean War, 12.

12 Truman, Memoirs, vol. 2, 376.

13 Quoted in Acheson, The Korean War, 73; Hennessey, Britain’s Korean War, 100.

14 William Stueck, Rethinking the Korean War: A New Diplomatic and Strategic History (Princeton: Princeton University Press, 2002), 126–127.

15 Hennessey, Britain’s Korean War, 3–4, 108–166; Stueck, The Korean War, 127–157.

16 Allan R. Millett, The War for Korea, 19501951: They Came from the North (Lawrence: University Press of Kansas, 2010), 297–299.

17 Ibid.

18 Stueck, The Korean War, 90–91.

19 Stueck, Rethinking the Korean War, 117; Hennessey, Britain’s Korean War, 69–104.

20 Hennessey, Britain’s Korean War, 69–104.

21 Ibid., 90.

22 Ibid., 93.

23 Ibid., 96.

24 Ibid., 91.

25 Ibid., 93.

26 Ibid., 90.

27 Ibid., 98.

28 Truman, Memoirs, vol. 2, 395.

29 Ibid.

30 Stueck, The Korean War, 130–132.

31 Ibid., 138.

32 Hennessey, Britain’s Korean War, 127–128; Truman, Memoirs, 413.

33 Stueck, Rethinking the Korean War, 129.

34 Ibid.

35 Stueck, The Korean War, 151–153.

36 Ibid., 151–152.

37 Ibid., 152–154.

38 Hennessey, Britain’s Korean War, 159–166.

39 Stueck, The Korean War, 155–156.

40 For an example, see Callum MacDonald, Britain and the Korean War (Oxford: Basil Blackwell, 1990).

41 Peter Lowe, Containing the Cold War in East Asia: British Policies Towards Japan, China, and Korea, 194853 (Manchester: Manchester University Press, 1997).

42 Stueck, Rethinking the Korean War, 129.

43 Peter Stueck, “The Korean War,” in The Cambridge History of the Cold War, vol. 3, ed. Melvyn P. Leffler and Odd Arne Westad (Cambridge: Cambridge University Press, 2010), 285–287.