Short answers, pulled from the story.
The Battle of Xuzhou was a military campaign between the Empire of Japan and the Republic of China fought in early 1938 during the Second Sino-Japanese War. It lasted more than three months, with fighting concentrated along the Jinpu and Longhai railway lines in Jiangsu and surrounding provinces.
Xuzhou was the midpoint of the Jinpu Railway and the intersection with the Longhai line, China's main east-west rail corridor running from Lanzhou to Lianyungang. Controlling the junction gave either side the ability to move troops rapidly across central China in both directions.
The Battle of Taierzhuang, fought between the 22nd of March and the 7th of April 1938, was the first major Chinese victory of the Second Sino-Japanese War. Forces under Li Zongren, Sun Lianzhong, and Tang Enbo defeated three Japanese divisions commanded by General Itagaki Seishiro in close-quarters urban fighting, with both sides losing approximately twenty thousand men.
Beginning on the 15th of May 1938, Li Zongren ordered between two hundred thousand and three hundred thousand troops in forty divisions to move south and west at night, hiding in wheat fields by day. A sandstorm and fog on the 18th of May helped conceal the retreat, and the breakout was complete by the 21st of May.
Chinese forces breached the Yellow River dikes in central Henan in May 1938 to halt the Japanese advance, which had reached within forty kilometers of Zhengzhou. The resulting flood inundated approximately fifty-four thousand square kilometers, killed an estimated four hundred thousand to five hundred thousand people, and created three million to five million refugees.
Japan captured Xuzhou on the 19th of May 1938 but failed to destroy the Chinese army, which broke out of the encirclement and later contributed roughly fifty percent of the forces that defended Wuhan. China lost the city but gained morale from the victory at Taierzhuang, and the Yellow River flood delayed the Japanese advance at enormous civilian cost.