Short answers, pulled from the story.
The 1938 Yellow River flood was deliberately created by the Chinese National Revolutionary Army, which destroyed the dike at Huayuankou on the 5th and the 7th of June 1938 by tunneling through it. Commander-in-chief Chiang Kai-shek sanctioned the operation on the 1st of June 1938 to slow the advancing Imperial Japanese Army.
Immediate drowning deaths were estimated at between 30,000 and 89,000. Total deaths from drowning, famine, and plague were estimated at between 400,000 and 500,000 by researchers Wang Zhibin (1986) and Bi Chunfu (1995). The Nationalist government's 1948 relief statistics claimed 893,303 deaths, a figure later discredited for its unspecified methodology.
NRA commanders had three strategic goals: protecting the Longhai railway supply route from the Soviet Union through Shaanxi, blocking Japan's path into Sichuan and the wartime capital Chongqing, and destroying railway infrastructure on the Beijing-Wuhan, Tianjin-Pukou, and Longhai railways. In the short term, the flood also aimed to halt Japanese units advancing toward Wuhan.
Yes, largely. Japan's Operation 5 never captured Shaanxi, Sichuan, or Chongqing. The flood denied Japan the Zhengzhou railway junction, destroyed the Bengbu railway bridge, and prevented rapid Japanese troop movements across North and Central China. It also bought time for the Battle of Wuhan.
The flood lasted from June 1938 to January 1947, nearly nine years. The dike breach was not permanently repaired until March 1947, after an initial repair in June 1946 was destroyed by summer flows. Five million civilians lived on inundated land throughout this period.
Yes. The Nationalist government initially claimed the flood was caused by Japanese aerial bombing, and used that story to justify inflated figures of 12 million displaced peasants to boost anti-Japanese sentiment. The actual cause was the deliberate destruction of the Huayuankou dike by the Chinese National Army.