The Soviet Border Service started to report an intensifying Chinese military activity in the region in the early 1960s. Tensions at first built slowly, but the Cultural Revolution made them rise much faster. The number of troops on both sides of the Sino-Soviet border increased dramatically after 1964. Militarily, in 1961, the Soviets had 225,000 men and 200 aircraft at that border. In 1968, there were 375,000 men, 1,200 aircraft and 120 medium-range missiles. China had 1.5 million men stationed at the border and had tested its first nuclear weapon (the 596 Test in October 1964, at Lop Nur basin). Both sides' political rhetoric was increasingly hostile.