By the time Tang slipped out of the city, however, the entire Nanking Garrison Force was rapidly disintegrating with some units in open flight. Furthermore, contact had already been lost with many units who thus never received Tang's message and continued to hold their positions as ordered, though even those that did receive it had little luck at slipping through the Japanese lines. China's 66th and 83rd Corps made a bid to evade the Japanese as planned through a gap to the east but immediately ran into their own minefield. After that they were attacked in flight by Japanese units and lost two divisional chiefs of staff in combat. Though the two corps had started the battle at least 11,000 men strong, only 600 of them escaped Nanking. Near dawn on December 13 a portion of China's 74th Corps was also annihilated in a bid to break through Japanese lines along the Yangtze River south of Nanking.