[This answer was written for a recent question about a graphic photograph purporting to show a soldier killed in the events of 6/4. This photo is one of a small number of photographs of the events which are often posted on reddit and elsewhere. Several of these photos match the gruesome deaths of several soldiers during the events in question. As such, parts of my answer are graphic.]

The Tiananmen Square protest or massacre is often used as the catchall English name for a sequence of nationwide unrest in China which began on April 15, 1989, and continued until early June. Tiananmen square in Beijing became the epicenter of the protests, hosting as many as 1 million protestors and spectators. The square was cleared of protestors in the early hours of June 4, but new protests stemming from the violence used to suppress the protests continued in many Chinese cities until June 10.

China in 1989 had been changed dramatically by a decade of Deng Xiaoping’s reforms. The “Open Door” policy and SEZs had been established; agricultural communes had been dissolved; and easing of price controls had caused dramatic inflation. Economic change had also produced new opportunities for official corruption and sparked a “crisis of faith” among intellectuals. These changes reached an inflection point in the mid 1980’s, with two waves of nationwide student protests in 1985 and 1986/87. The protests were influenced by the global backdrop of Glasnost/Perestroika (The Berlin wall fell sixth months after the protests, and the Warsaw pact and USSR dissolved in the two years after that) but the larger causes were domestic.

There was a liberal faction in the CCP in the 1980s centered on General Secretary Hu Yaobang and Premier Zhao Ziyang. The same two men being groomed by Deng Xiaoping as his potential successors. The liberal faction championed economic liberalization, advocated for certain forms of political liberalization, and was associated with a high-level anti-corruption campaign which alienated many powerful Party figures. A conservative backlash began manifesting in the mid-80s, ultimately forcing Hu Yaobang to resign as General Secretary in 1987. The sudden death of Hu Yaobang in 1989 was the inciting incident for the protests. As student outpourings of grief turned into mass gatherings, protests, and hunger strikes.

The protests stretched over many weeks due to significant disagreement within the government about how to respond. Whether to negotiate or use force, and how much force to use. The Government ultimately declared Martial law in mid-May and tried to send in thousands of troops. The public response to the declaration was highly negative. Sympathetic crowds blocked the military from entered Beijing, several military officers refused to follow orders. It took another ten days before troops entered the capital by force and cleared the square.

This disagreement was mirrored within the protest movement. No organization is monolithic, but these protests involved vast numbers of students and other citizens. There were those who wanted democratization; those who wanted less or more economic liberalization; and those concerned with the timeless grievances of government corruption and graft. While the ASUBU/AFS was loosely in control among the students in Tiananmen square, there were divisions among the students from the capital and those who had travelling in from other cities. Divisions among student and non-student protesters. And a distinction between those actively protesting and other citizens who only occasionally came out in support of the protests. In the subsequent events of June 3-4 most violence involved angry crowds in disparate parts of Beijing, responding to troop movements, violence, and rumors of violence. The makeup of these crowds and the extent of student involvement and ASUBU involvement/direction is completely unknown in most instances, but there is little evidence ASUBU directed anything outside of the square itself.

Despite the sometimes nebulous or contradictory objectives of the protests, they had widespread support which extended even to some senior party figures and military units. Unscientific contemporary polling indicated roughly 60% of the population supported the right of the students to protest, with only 10% opposed. The protestors’ complaints about corruption and inflation were relatively universal. Furthermore, the vagueness of the demands allowed many to project their own long-simmering discontents onto the protests. The protests also captured anxieties and disagreements about the future direction of China which divided senior Party leaders and every level of society. The protests ultimately involved more than a million people, protests of more than 10,000 people in dozens of cities, and the mobilization of more than 200,000 troops to end the protests.

The suppression of the Protests

These protests, and their suppression, are often referred to in English as the “Tiananmen Square Massacre,” but it is likely that only about a dozen deaths occurred in the Square itself, with most of the killing happening around the Muxidi Bridge (about 6 km to the west).

Some key events relevant to this question:

• At 10pm on June 3 troops were ordered into the city from the surrounding suburbs. Angry crowds quickly assembled, The majority of deaths happened around Muxidi, where the crowd began pelting the advancing troops with rocks. Troops fired in the air, and when this had little effect, began firing into the crowd.
• Crowds being reinstalling barricades which had been pushed aside by troops in some places. Although crowds had used buses to block the streets prior to this, around 11:40pm there are reports of these bus barricades being set of fire.
• As gunfire can be heard, civilian casualties multiply, and rumors spread through the city of the martial law troops killing citizens; the violence from the crowds escalates. There are numerous reports of people in the crowd setting fire to army trucks, APCs, and buses carrying troops. Burning as many as 500 trucks and in a few cases throwing Molotov cocktails.
• Numerous soldiers are isolated from their units or ‘kidnapped’ by the crowds, several of these soldiers are alleged to have been killed in quite graphic ways. With their corpses being subsequently mutilated in a few cases.