Between 1965 and 1969, the Soviets had been sending forces to the disputed regions. Along the border with China, the Soviet forces swelled from 13 to 21 divisions, posing a new military risk to the Chinese. The Red Guards had undermined the power of the military during 1967 and 1968, with Jiang Qing further exacerbating the sentiment against the military. With a weakened military that was wary of Chinese leadership, Mao was now faced with the prospect of war with their former ally, who found themselves in a greater position of power compared to the Chinese.

As the Soviet military built up its forces on the border, it became obvious that China could not continue to operate solely on its own. Faced with a military threat internally and externally, China stopped seeing the US as its greatest military threat and instead began to recognize that the Soviet Union posed a much greater risk. The imminent threat that the Soviet Union presented was realized in 1969 when the two sides began skirmishing along the borders.

In March 1969, the border clashes moved to a small island known as Zhenbao Island in China and Damansky Island in the Soviet Union. On March 2nd, 1969, the Chinese forces ambushed the Soviets stationed on the island. The Soviets were taken by surprise since the Chinese soldiers approached them with no guns. Before the Soviets could react, though, the Chinese soldiers pulled back their coats, showing that they were, indeed, armed. Taken by surprise, the Soviets had no chance to react as Mao's men mowed down all seven of them. Behind the initial Chinese advance, 300 more soldiers of the People's Liberation Army emerged and began shooting at the other Soviets stationed on the island.

The Zhenbao/Damansky Island incident highlighted a problem that Mao had been ignoring. For years, he had attempted to be a communist leader, standing alone in the world. The open conflict with the Soviet Union proved that this was not a viable option in the changing world. China was large, but it could not stand alone and turned to the US. This allowed the US to bolster its position regarding the Soviet Union and even led to the meeting of President Nixon with Mao in China.