Soon after, while serving in the Special Red Banner Far Eastern Army under Vasily Blyukher, he took part in the Russo-Chinese Eastern Railroad War of 1929–1930 when the Soviet Union intervened to return the Chinese Eastern Railway to joint Chinese and Soviet administration, after Chinese warlord Zhang Xueliang of the Republic of China attempted to seize complete control of the railway. It was in the early 1930s that Rokossovsky's military career first became closely intertwined with Semyon Timoshenko and Georgy Zhukov, when Rokossovsky was the commander of the 7th Samara Cavalry Division, Zhukov as a brigade commander under him and Timoshenko his superior Corps commander. Both became principal actors in his life during World War II, where he served directly under both at different times. A sense of the nature of the beginning of Rokossovsky's famous World War II rivalry with Zhukov can be gathered from reading Rokossovsky's comments in an official report on Zhukov's character: Has a strong will. Decisive and firm. Often demonstrates initiative and skillfully applies it. Disciplined. Demanding and persistent in his demands. A somewhat ungracious and not sufficiently sympathetic person. Rather stubborn. Painfully proud. In professional terms well trained. Broadly experienced as a military leader... Absolutely cannot be used in staff or teaching jobs because constitutionally he hates them. Rokossovsky was among the first to realize the potential of armoured assault. He was an early supporter of the creation of a strong armoured corps for the Red Army, as championed by Marshal Mikhail Tukhachevsky in his theory of "deep operations". Purge and rehabilitation Rokossovsky held senior commands until August 1937 when he became caught up in Joseph Stalin's Great Purge and was accused of being a spy. His association with the cutting edge methods of Marshal Tukhachevsky may have been the cause of his conflict with more traditional officers such as Semyon Budenny, who still favoured cavalry tactics over Tukhachevsky's mass armour theories, but few historians believe that the purge of the Red Army was solely a dispute over policy, and most attribute the purges to political and military rivalries as well. Some officers were merely swept up on suspicion due to past associations; in Rokossovky's case his association with the Special Red Banner Far Eastern Army and the intrigues surrounding Marshal Vasily Blyukher, who was arrested shortly after Rokossovsky and who died in prison without confessing, may have been enough to trigger his arrest.