Short answers, pulled from the story.
The Northern Expedition was launched by the National Revolutionary Army of the Kuomintang to reunify China, which had fragmented following the 1911 Revolution. The campaign targeted the Beiyang government in Beijing and the regional warlords who controlled much of the country.
Generalissimo Chiang Kai-shek led the Northern Expedition. He resigned as commander-in-chief on the 12th of August 1927 and went into exile in Japan following a political split within the KMT, then resumed command on the 1st of January 1928 after rival factions agreed to recognize his leadership.
The Shanghai Massacre took place between the 12th and the 14th of April 1927, when Chiang Kai-shek ordered the arrest and killing of hundreds of communists in Shanghai, using the Green Gang underworld to eliminate trade unionists and CCP members. The purge ended the First United Front between the KMT and the Chinese Communist Party and triggered a political split between the rightist Nanjing faction and the leftist Wuhan faction of the KMT.
The Northern Expedition concluded when Zhang Xueliang, who had inherited leadership of the Fengtian clique after his father Zhang Zuolin was assassinated by the Japanese Kwantung Army, declared Manchuria's allegiance to the Nanjing government on the 29th of December 1928. Beijing had fallen to NRA forces on the 6th of June 1928, ending the Beiyang government.
Soviet advisors Mikhail Borodin and Vasily Blyukher devised the initial strategy for the KMT's advance, focusing first on defeating Wu Peifu while avoiding confrontation with Sun Chuanfang and Zhang Zuolin. Borodin also served as the official liaison between the KMT and Moscow, and he encouraged expansion of the CCP's influence within the KMT's left-wing faction.
The Jinan Incident began on the 3rd of May 1928 when a minor clash between Chinese and Japanese troops escalated on the 8th of May into a full Japanese assault on Jinan. During the incident, Japanese forces killed KMT foreign affairs commissioner Cai Gongshi, several diplomats, and approximately five thousand Chinese civilians.