1938 Yellow River flood The 1938 Yellow River flood ( ) was a flood created by the Nationalist Government in central China during the early stage of the Second Sino - Japanese War in an attempt to halt the rapid advance of the Japanese forces . It has been called the " largest act of environmental warfare in history . " The strategic decision and the flood . Following the onset of the Second Sino - Japanese War in 1937 , the Imperial Japanese Army marched rapidly into the heart of Chinese territory . By June 1938 , the Japanese had control of all of North China . On June 6 , they captured Kaifeng , the capital of Henan , and threatened to take over Zhengzhou , the junction of the arterial Pinghan and Longhai Railway s , and Japanese success would have directly endangered the major cities of Wuhan and Xi ' an . To stop further Japanese advances into the western and southern part China , Chiang Kai - shek , at the suggestion of Chen Guofu , determined to open up the dikes on the Yellow River near Zhengzhou . The original plan was to destroy the dike at Zhaokou , but due to difficulties at that location the dike was destroyed on June 5 and June 7 at Huayuankou , on the south bank . Waters flooded into Henan , Anhui , and Jiangsu . The floods covered and destroyed thousands of square kilometers of farmland and shifted the mouth of the Yellow River hundreds of miles to the south . Thousands of villages were inundated or destroyed and several million villagers driven from their homes and made refugees . An official Nationalist post - war commission estimated that 800 , 000 were drowned , which may be an underestimate . Controversy over the strategy . The strategic value of the flood has been questioned . Japanese troops were out of its range , either to the north and east or to the south . Their advance on Zhengzhou was halted , but they took Wuhan in October by attacking from a different direction . The Japanese did not occupy much of Henan until late in the war and their hold on Anhui and Jiangsu remained tenuous . Most of the towns and transport lines in the areas which were flooded had already been captured by the Japanese ; after the flood they could not consolidate their control over the area , and large parts of it became guerrilla areas . Controversy over the number of casualties . The number of casualties in the flood remains disputed and estimates have been revised by the Chinese government and other researchers in the decades after the event . There is no way of accurately assessing the casualties : much of the population , including officials had already fled , leaving no government control and no one to count the dead . In the shifting battles between bandits , Nationalists , Communists , and Japanese , counting casualties was not a high priority . The government , after initially claiming that the breach was caused by Japanese bombing , used the heavy casualties to demonstrate the scale of sacrifice required of the Chinese people . They claimed that 12 million people had been affected by the flood , and in 1948 it estimated the number of deaths at 800 , 000 . A 1994 official history of the war put the dead in the flood at 900 , 000 and the refugees at nearly 10 million . Scholars exploring the archives now give much lower figures : 400 , 000 – 500 , 000 dead , 3 million refugees , and 5 million people affected ( another estimate puts the number of dead at 500000 , and the number of homeless at 500000 ) . Aftermath . Besides the massive death toll , the flooded areas were affected for years to come . The flooded countryside was more or less abandoned and all the crops destroyed . Upon the recession of the waters much of the ground was uncultivable as much of the soil was covered in silt . Many of the public structures and housing were also destroyed , leaving any survivors destitute . The irrigation channels were also ruined , further adding to the ecological toll on the farmlands . The destruction also had an adverse effect on the Chinese population . Unable to fully decide which group deserved more blame for the catastrophe , the Chinese Government or the invading Japanese , many survivors blamed both sides . The flooded areas became fertile recruiting grounds for the Chinese Communists , using their anger towards a shared enemy to bring them into their ranks . By the 1940s they had evolved into a major guerrilla base known as the Yuwansu Base Area . The breach in the dam became such a major rallying point for the Communists that they actually tried to halt an attempt by the Chinese Government , with the assistance of the UN , to seal the breach . Their armed resistance ultimately failed and the dikes were rebuilt in 1946 and 1947 and Yellow River returned to its pre - 1938 course . The point was nevertheless made , the breach had in the end given the Communists a huge boost in the North .