<P> Though the Soviet Union never acknowledged its participation in the conflict, it is clear that many suspected it . </P> <P> Soviet pilots, though forbidden from communicating in any language other than basic Korean across their radios, often resorted to Russian when stressed or when swearing . This was picked up by American pilots . Nevertheless, reports of covert Soviet involvement were always denied by the Soviet Union, and the United States was not inclined to press the issue so as to avoid escalating tensions further . It was only recent, through the publication of books by Chinese and Russian authors, such as Zhang Xiaoming, Leonid Krylov, Yuriy Tepsurkaev and Igor Seydov, that the extent of the Soviets' participation became clear . </P> <P> Contrary to expectations, the Soviet intervention in Korea did not inspire the Chinese leadership with confidence . Mao, in particular, felt betrayed that the Soviet leadership had refused to send infantry and armoured units, in addition to its MiG squadrons, and join the conflict openly beside China . There is evidence that the Chinese felt restricted by the Russians, who forced them to defer to the Soviet Union for technological and strategic support, but offered only minor support in exchange . Furthermore, the Chinese leadership felt humiliated by the Soviet decision to make the Chinese pay them for all the material support that they had received, which "made the Soviets seem more like arms merchants than genuine Communist internationalists ." </P> <P> In effect, Zhang Xiaoming argues that the Chinese came to feel that the Soviet Union was both an unreliable and demanding ally and took greater steps to ensure autarky from the USSR in the years following the War . In 1960, China broke from the Soviet Union in an event known today as the Sino - Soviet Split, creating a rift amongst all communist powers which were expected to pick one side of the divide . The North Korean regime, which bordered both countries, successfully navigated the split by playing one power off against the other . It did not firmly align with either power until the Soviet reforms under Mikhail Gorbachev compelled the regime to align with China . </P>

How important was russian intervention in the outbreak of the korean war