In June 1938, during a military meeting, Generalissimo Chiang Kai-shek authorized the opening of the Yellow River dikes near Zhengzhou. This action transformed the river into a weapon of war, aiming to delay the Japanese advance following the Chinese defeat at the Battle of Xuzhou. The Nationalist army, seeking to buy time, employed a strategy of "using water instead of soldiers." The southern dike of the Yellow River at Huayuankou in Henan province was breached on June 5 and 7, 1938, after initial attacks on a site further upstream. The breach was chosen for its potential impact on Japanese progress. The Yellow River abandoned its usual course and flowed into the Huai River basin, remaining there until 1947. This diversion redrew the hydraulic geography of three provinces and affected 20 counties directly. Approximately 5 million civilians lived in the flooded area, with 32 percent of agricultural land and 45 percent of villages submerged. The immediate human toll ranged between 30,000 and 89,000 drowners. However, the disaster continued with famine and epidemics, leading to an estimated 400,000 to 500,000 deaths. This episode is considered one of the deadliest disasters deliberately caused by an army during wartime. The Japanese advance toward Wuhan was delayed but not stopped, as enemy troops bypassed the flooded area and continued their offensive. Restoring the Yellow River to its original course required significant effort, taking until 1947. The diversion caused long-term environmental damage, with soil impoverished by the salt and sand carried by the diverted waters. This event remains a significant example of environmental warfare, where a river's use as a weapon led to uncontrollable damage.