Short answers, pulled from the story.
Chiang Kai-shek led the Nationalist government forces while Yan Xishan, Feng Yuxiang, and Li Zongren commanded the opposing anti-Chiang coalition. Zhang Xueliang initially remained neutral before declaring support for Chiang on the 18th of September 1930.
The conflict occurred between 1929 and 1930 with major offensives launching on the 11th of May 1930. Hostilities effectively ended when Yan Xishan and Feng Yuxiang announced their resignations from all positions on the 4th of November 1930.
Tensions rose after the National Demilitarization Conference failed in January 1929 due to accusations that Chiang Kai-shek sought to centralize military power. Li Zongren and Bai Chongxi broke relations with Chiang in March 1929 following his appointment of a new governor to Hunan province.
More than one million soldiers fought across Henan, Shandong, Anhui, and other areas during the largest conflict at Xuzhou. Initial forces included over 700,000 coalition soldiers facing 295,000 National Revolutionary Army troops.
Combat spread across multiple provinces including Henan, Shandong, Anhui, Gansu, and Shanxi along the Longhai Railway. Major engagements occurred near Kaifeng, Xuzhou, Jinan, and Yueyang before Zhang Xueliang's intervention shifted control north of the Yellow River.