The Republicans rallied behind MacArthur who did not stifle his view that America should attack enemy bases in China, even at the risk of a wider war. Truman was incensed. The battle in Washington was soon drawing bigger headlines than the battle in Korea. (Ibid)
Many theorists in the 1950's saw the Chinese involvement as being part of an overall communist plot to dominate the world. They saw little distinction between Chinese and Russian involvement in the Korean War but rather saw the war as a combined effort at communist dominance.
In the 1950s, Western scholars, strongly influenced by the intensifying Cold War, generally viewed China's entrance into the Korean War as a reflection of a well-coordinated Communist plot of worldwide expansion, believing that the entire international
Communist movement was under the control of Moscow, and that neither Beijing nor Pyongyang had the freedom to make their own foreign policy decisions. The Korean conflict, therefore, was seen as an essential part of a life-and-death confrontation between the Communists on the one hand and the "free world" on the other.
These theorists were convinced that Beijing's involvement in the Korean
War was part of Moscow's overall Cold War strategy. However, this view was challenged by researchers and theorist like Allen S. Whiting who believed that the suggested close unity between Russia and China in the Korean conflict was erroneous and that China was not involved in the initial planning of the conflict and had in fact attempted to halt the conflict.
After the outbreak of the Korean War, Whiting believed, Beijing tried to terminate the conflict through political settlement, and only after the attempts for a political solution failed in late August 1950 did Beijing begin necessary military preparations in early September.
In his analysis Whiting used resources from newspapers and journals of the time as well as Western intelligence resources to come to these conclusions. This would suggest that China did not have as much influence on the cause and event of the Korean War from a political point-of-view as the Russians. Whiting goes on to suggest from his sources that it becomes clear that China was in fact actively opposed to the enlargement of the conflict and went to some lengths to avoid any escalation. He suggests that Beijing entered the war only after Washington had ignored all warnings of the escalating conflict. To the Chinese the actions of Washington and General Douglas MacArthur, in proceeding with the conflict, indicated that the safety of the Chinese-Korean border was in danger. (ibid) Whiting also posits that the central reason for Chinese involvement in the Korean crisis was that they saw America as a threat to their national security, and not because they were involved in a plot with the U.S.S.R. For world dominance. (ibid)
This view was later endorsed by many researchers in the field who claimed that Chinese involvement was mainly due to fears about their security, more than anything else. "Building on Whiting's thesis, scholars paid more attention to Chinese Communist Party (CCP) leaders' concerns for China's national security as the decisive factor underlying their decision to enter the Korean War." (ibid)
Theorists also bolstered this argument by stating that China could ill afford a war at that particular stage of its development as it faced a difficult period of both political and economic reconstruction. (ibid) China was also involved with the problem of "liberating" nationalist controlled Taiwan. (ibid) They also contend that if the U.S. forces had not crossed the 38th Parallel then China would not have become embroiled in the conflict as it would not have perceived the United Stated as threat to its own security. This view is further endorsed by other readings of the Chinese involvement in the war.
PRC's intervention in Korea was primarily precipitated by its own security concerns. In his telegram to premier Zhou Enlai on Oct. 13, 1950, Chinese leader Mao Zedong summarized the rationale for sending troops to repel advancing U.S. forces: if PRC did not take the initiative, then U.S. forces would press on China along the Yalu river, China's northeastern defense force would be pinned down, Southern Manchuria's power supply (generated from hydroelectric plants in North Korea) would be controlled by hostile forces, and the situation would have resulted in the uprising of domestic and international "reactionary elements." (Dongxiao Yue,)
In contrast to this theory there are other academics who question a too simplistic analysis of Chinese motives in entering the Korean War. They see a complex set of factors that are related to the way that China perceives itself in the international areas at that time.
In this regard one could also include the fact that the decision to go to war was also influenced by the already poor relationship and distrust between Russia and America, particularly with regard to the Unites States support for an independent Taiwan. In essence these theories suggest that the influence of China on the caused of the Korean War were not as significant as Russian involvement. China however had an obviously greater direct military influence on the war than the Soviet Union, and seen from this perspective, China's influence was extremely influential in determining the events and outcome of the war. But as Perpaoli clearly states, "Contrary to western wisdom, the Soviet Union did not mastermind the Chinese participation in the war. Stalin refused to offer much support to the Chinese. China had to pay for all its weapon purchases from USSR plus interests."(Pierpaoli, Paul G., Jr.)
Therefore, if we are to discount the theory that Russia and China planned the war as a combined "plot" against the West then it would seem that Russia and the perceived communist threat was the main and underlying influence in the war, while China was more influential in the military sphere. This view is underlined by the following observation:
North Korean leader Kim Il-sung and Chinese communist leader Mao Zedong, while primarily concerned with their own objectives and national interests, shared a communist ideology and were bound by the historical connection and geographical proximity between China and Korea. Their common perception that they were threatened by anti-communist forces led by the United States also influenced their actions.
Two Chinese scholars, Chen Jian in China's Road to the Korean War: The Making of the Sino-American Confrontation, and Zhang Shu Guang in Mao's Military Romanticism: China and the Korean War, 1950-1953, focusing on China's role in the war state that they are both in agreement that "... By the time of the North Korean attack on 25 June 1950, the Chinese leadership had long-since concluded that the United States was China's primary enemy and that a military conflict was likely." (ibid)
These authors also mention that China was also motivated by a desire to restore their role as a world power. They regard this aspect as another reason why China become involved in the Korean War.
Russian influence on the one hand was certainty part of the overall cause of the Korean War. The Soviet government was intent on an expansionist strategy that involved many theatres of concern. It is unlikely that the Korean War would have started if there had not been the perception of the communist threat and the awareness of Russian ideal of expansion. The consensus among researchers seems to indicate that the Russian role in the Korean War was part of their expansionist strategy.
The USSR, also, went to war because of the Cold War. Stalin wanted to see Communism expand as long as he did not get involved in a 'hot war' with America. In 1949, Kim II Sung visited Stalin. He persuaded Stalin that he could conquer South Korea. Stalin did not think that America would get involved, so he gave his agreement. Kim II Sung also went to see Mao Tse Tung, the leader of China, to get his support.
Why did the Korean War break out in 1950?)
From a general historical point-of-view it could be argued that in real terms, and in an ideological sense, Russia through its political strategies and anti-American rhetoric was more influential than China in starting the Korean War.
Stalin's rhetoric was becoming increasingly more critical of the West stating that World War II was the fault solely of the capitalist system and that without change there would be similar 'crises and military catastrophes.' The nature of Soviet rhetoric becoming more aggressive along with their increasing advances on gaining strategic territory in Iran and Turkey led to an increasing fear of communist influence throughout Europe.
It was this aspect that the United States reacted against and it was the fear of global communist dominance which was the most obvious cause of the war- notwithstanding the many other complex factors.
The Korean War Revisited. 1998. Accessed November 20, 2004. http://www.mtholyoke.edu/acad/intrel/korrev.htm