Japanese soldiers marched from Shanghai to Nanking at a breakneck pace, rapidly defeating pockets of Chinese resistance. By December 9 they had reached the last line of defense, the Fukuo Line, behind which lay Nanking's fortified walls. On December 10 Matsui ordered an all-out attack on Nanking, and after less than two days of intense fighting Chiang decided to abandon the city. Before fleeing, Tang ordered his men to launch a concerted breakout of the Japanese siege, but by this time Nanking was largely surrounded and its defenses were at the breaking point. Most of Tang's units simply collapsed, their soldiers often casting off their weapons and uniforms in the streets in the hopes of hiding among the city's civilian population.