In the spring of 1989, Chinese pro-democracy activists filled Beijing's Tiananmen Square. For weeks, the protesters, led by students, stood in unprecedented defiance of the Communist regime. They called for respect for human rights and greater political participation amid the ambitious economic reforms spearhead by then-leader Deng Xiaoping. The protests eventually spread to 400 cities across China. Communist Party leaders, however, saw the protests as a threat to their hold on power and the political system. On the morning of June 4, the government sent armed troops to dissolve the demonstration in Tiananmen Square, killing and arresting activists. Though there is no official death toll, estimates range from several hundred to more than 10,000. The day is thought to be one of the bloodiest political crackdowns in modern history.