The film focuses on an epic battle in the history of China's War of Resistance against Japan, which shocked the world with its overwhelming force against a small enemy. In the 1944 Hengyang defense battle, the 10th Army of the Chinese front battlefield, with a force of less than 18,000 people, defended the city alone against the Japanese army with a total strength of 110,000 people outside the city for 47 days. The Chinese army suffered more than 16,000 casualties and the Japanese army suffered more than 48,000 casualties, creating the only record of the comparison of enemy and our forces and casualties since the War of Resistance. It dealt a heavy blow to the Japanese army's No. 1 operation launched by the Japanese headquarters and became a battle case comparable to any battle in World War II.

1944年6月，日军欲在三日之内攻陷衡阳。国民政府命守军坚守七天，等待援军。在守军通讯营被日军炸毁后只剩下了一个电台，而电台成了唯一通往外界的通道，也造就衡阳守军坚守47天的奇迹。