Short answers, pulled from the story.
The New Fourth Army Incident, also called the Wannan Incident or South Anhui Incident, occurred in January 1941 in southern Anhui province, China. A Nationalist force of around 80,000 troops surrounded and attacked a Communist New Fourth Army column of roughly 9,000 soldiers, killing political commissar Xiang Ying and allowing only about 2,000 to escape.
The Second Sino-Japanese War had nominally suspended the Chinese Civil War through a United Front agreement, but tensions persisted. In December 1940, Chiang Kai-shek ordered Communist forces to withdraw north of the old Yellow River track. The Communists only partially complied, agreeing to move the Wannan troops to the northern bank of the Yangtze River, which the Nationalists treated as insubordination.
Shangguan Yunxiang commanded the Nationalist force of 80,000 that surrounded the Communist column at Maolin Township. The New Fourth Army's commander was Ye Ting, who was detained when he went to Shangguan's headquarters to negotiate on the 13th of January 1941.
Ye Ting was detained when he traveled to Nationalist headquarters to negotiate, then sent to a military tribunal after Chiang Kai-shek ordered the New Fourth Army disbanded on the 17th of January 1941.
On the 20th of January 1941, just three days after Chiang Kai-shek ordered the army disbanded, the CCP in Yan'an ordered its reorganization. Chen Yi was named the new commander and Liu Shaoqi became political commissar. The reconstituted force combined with the Eighth Route Army to form a structure of seven divisions and one independent brigade totalling over 90,000 troops.
The novelist Mao Dun wrote a story called Fushi about the New Fourth Army Incident, making it one of the few episodes of the Chinese Civil War to receive direct literary treatment from a major Chinese writer.