An Explanation of U.S. Entrance Into the Korean War

An Explanation of U.S. Entrance into the Korean War

Eric Gilbertson

17.40 American Foreign Policy Fall 2004

In this paper, I give an explanation of why the U.S. entered the Korean War and how U.S. policy was influenced by the assumption that the Soviet Union initiated the conflict. I argue that the U.S., thinking the USSR used North Korea as a proxy to attack American-controlled South Korea, intervened in the conflict to prevent the Soviet Union from gaining world power and influence. There are many reasons why the United States would have sought to limit Soviet power in the world, and I focus on the two I find most compelling. First, the U.S. believed in the strategy of primacy[1], whereby world stability results from a global imbalance of power, preferably in favor of the U.S. Thus the greatest threat to peace would be the rise to power of a competitor nation to the U.S., such as the Soviet Union. Second, the U.S. believed in the offense-defense theory, outlined by Robert Jervis, and in particular, in his hypothesis that war is more likely when conquest is easy[2]. If the Soviet Union met little resistance from attacking South Korea, it would likely try to gain more power by extending its borders into other regions such as Eastern Europe and the Mid-East, and world war would soon break out. Based on these reasons I draw the conclusion that the U.S. retaliated against the North Korean invasion to thwart the Soviet Union’s quest for world power, and to thus decrease the chances of a new world war.

This paper is laid out in three sections. Section I explains how the U.S. entered the Korean War to maintain world primacy. Section II covers the argument that the U.S. sought to make conquest more difficult for the Soviet Union, and thus make world war less likely. Section III examines two alternative theories on why the U.S. entered the Korean War: first, that policymakers were following the Truman Doctrine to support any free peoples resisting subjugation by outside forces. Second, that the U.S. wanted to contain communism and believed in the Domino Theory, which predicted more states to fall to the communists if South Korea fell.

I. Primacy Argument

The U.S. entered the Korean War to maintain its primacy over the Soviet Union. According to the primacy theory, peace is a result of an imbalance of power. If one state is much stronger than any competitors, then this state can effectively deter any potential aggressors from initiating conflicts, and the world will thus be more stable. In 1950, near the beginning of the Korean War, the United States was certainly the most powerful state among all the Super Powers (USSR, UK, France, Japan, Italy, and West Germany): the U.S.’s Gross National Product was over twice that of its nearest competitor (the USSR), it produced nearly one third of world manufacturing output, its military armament and aircraft production from WWII was nearly three times that of the USSR, and its relative war potential was the highest in the world[3]. The U.S. understandably wanted to maintain this dominance, and this fact is evident from its actions near the end of WWII.

In 1947 the U.S. assumed (incorrectly) that the USSR was funding pro-Soviet revolutionaries in Greece, and intervened to prevent a revolution that it thought would increase Soviet power. At the Potsdam Summit in 1945 America refused to allow the USSR territorial gains from the Axis powers of the War (specifically, territory in Turkey, Japan, and Libya)[4]. These actions showed that the United States wanted to maintain the current balance of power in the world and not tip it in favor of any other state, not even its ally from the war.

While the United States favored the status quo of world power, the Soviet Union was eager to expand and challenge the U.S. for dominance. In 1944 Joseph Stalin successfully took over Poland from the defeated Germany, agreeing with the U.S. to allow Poland a democratic government but actually installing a pro-Soviet one. In 1945 the USSR, who had by treaty been temporarily occupying Iran, backed a rebellion that, if successful, would have given them permanent power in the region. However, under pressure from the U.S. and U.N. the Soviets eventually pulled out of the country (in 1946) as dictated by the treaty[5].

These historical actions are very relevant in explaining U.S. reactions to the Korean War. When most officials in the Truman administration, including Secretary of State Dean Acheson, learned on June 24, 1950 that North Korea had crossed the 38th parallel and invaded the South, they assumed it could only have taken place with Soviet authorization[6]. According to one official, the relationship between the Soviet Union and North Korea was as close as “Walt Disney and Donald Duck”[7].

Truman officials assumed that the Soviet Union was thus challenging the U.S. for power in that region not directly but by proxy. The U.S. thought that Korea was sufficiently powerful that losing it could be just enough to tip the scale of power in favor of the USSR, forfeiting U.S. primacy. Thus the Truman administration had no option but to enter the Korean War to thwart the hegemonic Soviet Union.

II. Prevention of Offense-dominant World

The U.S. followed the offense-defense theory of Robert Jervis that war is more likely when conquest is easy, and sought to prevent Soviet conquest of Korea, thus limiting Soviet world power and the likelihood of war. According to offense-defense theory, in a world in which the offense has the advantage, states are more likely to pursue opportunistic expansion, because such expansion has a high probability of succeeding[8]. States also have much to gain and little to lose when conquest is easy (if they are unsuccessful they just return to the position they started in, but if they succeed they gain possibly valuable new territory). However, the instability in the world caused by this expansion cannot last long, and soon the non-expansionist states will retaliate against the aggressor state, leading to war.

As described in section I, when World War II ended the Soviet Union was eager to acquire new territory in Eastern Europe and the Mid-East, though it was only successful in gaining Poland, East Germany and North Korea. By 1950, however, an opportunity had arisen for the Soviets to claim more land.

Earlier that year Secretary of State Dean Acheson had given a speech in which he omitted South Korea from his description of America’s defense perimeter in Asia[9]. In 1949 the U.S. had pulled its troops out of South Korea to restation them in more important locations, leaving the South vulnerable to attack[10]. Thus the Soviets could very likely have interpreted the situation in South Korea as an open window for takeover.

In this case, the Soviets perceived conquest to be easy, and, in accordance with offense-defense theory, attempted opportunistic expansion by engineering an invasion of South Korea.

After the U.S. learned of the invasion of South Korea, it interpreted it as a test of U.S. credibility in the region and a first step towards Soviet world conquest.

Indeed, the U.S. had encountered similar situations, in which a lack of will of the U.S. to counter opportunistic expansion early ma have been a major factor in causing aggressors to reach further. Near the onset of WWII Hitler invaded Poland, Czechoslovakia, and other neighboring nations in part because he didn’t believe America posed any credible threat to his expansion, and thus conquest was easy. This ultimately led to world war, which America did not want to have repeated as a result of the new Korean crisis.

The best way to prevent a third world war, the administration reasoned, was to show the Soviets that America was determined to counter its opportunistic expansion, and that conquest in that region would be very difficult. Thus, the U.S. decided to enter the Korean War and prevent the Soviets from increasing the likelihood of war.

III. Truman Doctrine and Domino Theory

One alternative explanation of U.S. entrance into the Korean War is that it was trying to protect the free people of South Korea. According to the Truman Doctrine, outlined in 1947, the policy of the U.S. was “to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures.”[11] Proponents of this argument point out that supporting free peoples of states in such a position will encourage the states to look favorably on American ideology. These states will then be more likely to ally with the U.S. in times of war (and hence help the U.S. win the war) because they are more understanding of and agree with the U.S.’s policies. This is a result of Stephen Walt’s “birds of a feather flock together” theory that states of similar ideologies tend to ally together[12].

South Korea certainly fit the description of a free people – after WWII America had freed the South from Japan and installed a democratic government – and the North Koreans were definitely subjugating the South by invading. However, I don’t think this information alone convinced the U.S. to intervene in the War. First, not all officials in the Truman administration considered South Korea to be of strategic significance to the U.S. (Secretary of State Dean Acheson admitted this view in his 1950 speech to the Washington Press Club)[13], and if the U.S. had really wanted to protect its freedom it would have left a military peace-keeping force in the country for security. Second, U.S. administrators were biased against people of Asian nationality (as evidenced by the internment of Japanese-American citizens in concentration camps during WWII) and wouldn’t go out of their way to aid an East-Asian nation such as South Korea without ulterior motives.

Another possible explanation of U.S. entrance into the Korean War is that the U.S. believed in the domino theory and sought to prevent South Korea from becoming communist. (This theory was not officially framed until 1954, but its main points are applicable nevertheless). According to the Domino theory, if one nation fell to communism, others would also fall in rapid succession[14]. An increase in communist states would then pose a greater threat to free democratic states like the U.S., and world conflict could easily ensue.

Proponents of this argument point out historical evidence that the U.S. would fight communists attempting to take over free states: in 1947 the U.S. supported the Greek army against the communist EAM revolutionaries[15]; in Argentina that same year the U.S. sent military aid to suppress a pro-communist movement; and in 1948 the U.S. expressed tacit support for a democracy in communist Costa Rica[16]. Moreover, anti-communist sentiment in the U.S. was growing quickly, fuelled largely by the actions of Wisconsin Senator Joseph McCarthy, and this sentiment influenced national policy. In fact, Senator McCarthy actually charged President Truman of being “soft on communism”, causing Truman to drop in public opinion polls and giving him incentive to disprove this charge[17].

Despite these points I still argue that America did not intervene in Korea to stop the spread of communism. Other incidents of that era corroborate my claim. First, in Greece the main reason why the U.S. aided the Greek army against the EAM was because it thought the Soviets were supporting the revolution, not simply because the revolutionaries were communists. (In fact Stalin actually disliked the EAM, but the U.S. didn’t know this)[18]. Second, in 1949 the U.S. did nothing to oppose the rise of the communist People’s Republic of China[19]. I argue that this is because the Chinese acted independently of the Soviets (in Mao Zedong’s words the Soviets gave them “not even a fart” of aid), while the U.S. intervened in Korea because it strongly believed the Soviets had initiated that conflict.

Conclusion

I have evaluated the historical record and concluded that the U.S. most likely entered the Korean War to prevent the Soviet Union from gaining world power and influence. American and Soviet actions after WWII suggest that the U.S. desired to limit Soviet power for two reasons: first, so that the U.S. could maintain its military primacy and ensure world peace; and second, so that the U.S. could create a less offense-dominant world where Soviet conquest was more difficult and thus world war less likely.

[1] Barry R. Posen and Andrew L. Ross, “Competing U.S. Grand Strategies,” in Strategy and Force Planning (Newport, RI: Naval War College Press, 1995) pp 129-133.

[2] This argument is summarized in “Offense, Defense and the Causes of War”, manuscript by Sephen Van Evera, pp 1-36.

[3] Kennedy, P. 1987 “The Rise and Fall of the Great Powers: Economic Change and Military Conflict from 1500 to 2000. New York: Random House”

[4] Paterson, Clifford and Hagan, “American Foreign Relations,” pp 212-213

[5] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 238.

[6] (After WWII the U.S. and USSR had split Korea so that the Soviet Union controlled the North and the U.S. the South).

[7] Paterson, Clifford and Hagan , “American Foreign Relations” pg 268.

[8] Stephen Van Evera, “Offense, Defense, and the Causes of War,” pp 1-3

[9] Paterson, Clifford and Hagan, “American Foreign Relations” pg 267.

[10] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 253

[11] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 241

[12] Walt, S “The Origins of Alliances,” chapter 2 (“Explaining Alliance Formation) pp 17-49.

[13] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 267.

[14] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 242.

[15] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 242.

[16] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 256.

[17] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 268.

[18] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 242.

[19] Paterson, Clifford and Hagan, “American Foreign Relations,” pg 254.