While some 100,000 students marched on the streets of Beijing on 4 May to commemorate the May Fourth Movement and repeat demands from earlier marches, many students were satisfied with the government's concessions. On 4 May, all Beijing universities except PKU and BNU announced the end of the class boycott. Subsequently, the majority of students began to lose interest in the movement.
Students began the hunger strike on 13 May, two days before the highly publicized state visit by Soviet leader Mikhail Gorbachev. Knowing that the welcoming ceremony for Gorbachev was scheduled to be held on the Square, student leaders wanted to use the hunger strike there to force the government into meeting their demands. Moreover, the hunger strike gained widespread sympathy from the population at large and earned the student movement the moral high ground that it sought. By the afternoon of 13 May, some 300,000 were gathered at the Square.
On the morning of 13 May, Yan Mingfu, head of the Communist Party's United Front, called an emergency meeting, gathering prominent student leaders and intellectuals, including Liu Xiaobo, Chen Ziming and Wang Juntao. Yan said the government was prepared to hold immediate dialogue with student representatives, but that the Tiananmen welcoming ceremony for Gorbachev would be cancelled whether the students withdraw or not—in effect removing the bargaining power the students thought they possessed. The announcement sent the student leadership into disarray.
The students remained in the Square during the Gorbachev visit; his welcoming ceremony was held at the airport. The Sino-Soviet summit, the first of its kind in some 30 years, marked the normalization of Sino-Soviet relations, and was seen as a breakthrough of tremendous historical significance for China's leaders. However, its smooth proceedings was derailed by the student movement; this created a major embarrassment ("loss of face") for the leadership on the global stage, and drove many moderates in government onto a more 'hardliner' path. The summit between Deng and Gorbachev took place at the Great Hall of the People amid the backdrop of commotion and protest in the Square.
The situation seemed intractable, so the weight of taking decisive action fell on paramount leader Deng Xiaoping. Matters came to a head on 17 May, during a Politburo Standing Committee meeting at Deng's residence. At the meeting, Zhao Ziyang's concessions-based strategy was thoroughly criticized.
The movement, on the wane at the end of April, now regained momentum. By 17 May, as students from across the country poured into the capital to join the movement, protests of varying sizes were occurring in some 400 Chinese cities. Students demonstrated at provincial party headquarters in Fujian, Hubei, and Xinjiang. Without a clearly articulated official position from the Beijing leadership, local authorities did not know how to respond. Because the demonstrations now included a wide array of social groups, each carrying its own set of grievances, it became increasingly unclear with whom the government should negotiate, and what the demands were.
On the evening of 17 May, the PSC met at Zhongnanhai to finalize plans for martial law. At the meeting, Zhao announced that he was ready to "take leave", citing he could not bring himself to carry out martial law. The elders in attendance at the meeting, Bo Yibo and Yang Shangkun, urged the PSC to follow Deng's orders. Zhao did not consider the inconclusive PSC vote to have legally binding implications on martial law; Yang Shangkun, in his capacity as Vice Chairman of the Central Military Commission, went on to mobilize the military to move into the capital.
Li Peng met with students for the first time on 18 May in an attempt to placate public concern over the hunger strike. Li Peng said the government's main concern was sending hunger strikers to hospital. The discussions were confrontational and yielded little substantive progress or dialogue, but gained student leaders prominent airtime on national television.
On 19 May, the PSC met with military leaders and party elders. Deng presided over the meeting and said that martial law was the only option. At the meeting Deng declared that he was 'mistaken' in choosing Hu Yaobang and Zhao Ziyang as his successors, and resolved to remove Zhao from his position as general secretary. Deng also vowed to deal resolutely with Zhao's supporters and begin propaganda work.
The Chinese government declared martial law on 20 May and mobilized at least 30 divisions from five of the country's seven military regions. At least 14 of PLA's 24 army corps contributed troops. As many as 250,000 troops were eventually sent to the capital, some arriving by air and others by rail.
The army's entry into the city was blocked at its suburbs by throngs of protesters. Tens of thousands of demonstrators surrounded military vehicles, preventing them from either advancing or retreating. Protesters lectured soldiers and appealed to them to join their cause; they also provided soldiers with food, water, and shelter. Seeing no way forward, the authorities ordered the army to withdraw on 24 May. All government forces retreated to bases outside the city. While the Army's withdrawal was initially seen as 'turning the tide' in favour of protesters, in reality mobilization took place across the country for a final assault.