Xinjiang received aircraft, equipment for aviation, rifle-machine-guns and artillery workshops, uniforms, personal supplies, and other military equipment. Soviets also opened pilot schools to train local airmen. The Soviets also proposed the reduction of army to 10,000 men, but Sheng refused this proposal and instead reduced it to 20,000 men. In an agreement from 16 May 1935, ratified without consent from the Chinese government, the Soviet government provided substantial financial and material aid, including a five-year loan of five million "gold rubles" (Sheng actually received silver bullion). At about the same time, again without the consent from the Chinese government, Soviet geologists started a survey for Xinjiang's mineral resources. The result was Soviet oil drilling at Dushanbe. During Sheng's rule, Xinjiang's trade came under the Soviet control. The Soviet General Consul in Ürümqi was effectively in control of governing, with Sheng required to consult them for any decision he made. Alexander Barmine, the Soviet official responsible for supplying arms to Sheng, wrote that Xinjiang was "a Soviet colony in all but name". The Soviet stranglehold around Xinjiang was further enhanced through a secret agreement signed on 1 January 1936. The agreement included Soviet guarantee to come to the aid of Xinjiang "politically, economically and by armed force... in case of some external attack upon the province". By mid-1936, a significant number of Soviet specialists were active in Xinjiang involved in construction, education, health, and military training. The Russian language replaced English as the foreign language taught in schools. A number of Muslim youths, including Muslim girls, were sent to Soviet Central Asia for education. Sheng's government implemented atheistic propaganda, and Muslim women were encouraged to appear in public without a veil. Between 1934 and 1942, there were no significant relations between the Sheng's government and the Chinese government. However, with the German invasion of the Soviet Union, Sheng saw an opportunity to strike down Soviet proxies, the Chinese communists and to mend his relationship with the Chinese government now seated in Chongqing. Sheng had long prepared to purge the Chinese communists in Xinjiang. In 1939, his agents filled reports on clandestine meetings, the constant exchange of letters, and the unauthorized content of some of their propaganda. A month after the German invasion, in July 1941, the communist cadre had been demoted or cashiered. Chen Tanqiu, the chief liaison of the Communist Party of China (CCP) reported in Yan'an that his relations with Sheng became "extremely cold".