In OTL, Sun Yat-sen, the "Father of the Nation" (In the Republic of China) and the "Forerunner of the Revolution" (In the People's Republic of China) died of liver cancer on 12 March 1925 at Peking Union Medical College. In ATL, however, Sun Yat-sen battles through the illness, and instead dies three years later, at the end of the Northern Expedition, thus seeing the Kuomintang succeed to "unify" China by defeating the Warlord ruled Beiyang Government, and thus Sun Yat-sen dies a happy man. With Sun Yat-sen alive during the Northern Expedition, the Shanghai Massacre of 1927 never happens, causing the First United Front to never be split. (The Shanghai Massacre of 1927 never happens because the KMT and CCP both liked Sun Yat-sen and both were in a sense "united" under his leadership.) With the First United Front between the KMT and the CCP never broken, the OTL Chinese Civil War between the KMT and the CCP never happens, thus having a drastic change in history which will be further explored in this timeline.
On 12 March 1925 Sun Yat-sen "The Father of the Nation" and "The Forerunner of the Revolution" does not die of Liver Cancer as of OTL and instead begins a three year on and off battle against his Liver Cancer. With news that Sun Yat-sen did not die, the Kuomintang and the Chinese Communist Party both celebrate that this great man is still alive.
With Sun Yat-sen still alive, there is no power struggle in the KMT between Chiang Kai-shek, Wang Jingwei, and Hu Hammin. The remainder of the year is spent planning out the Northern Expedition between the united KMT and the united CCP. It is decided that Chiang Kai-shek, the Commander of the Whampoa Military, will lead the Northern Expedition, as in OTL, with his soon-to-be-ready troops being the main army force of the Northern Expedition.
On July 9th, (as in OTL), Chiang Kai-shek gave a lecture to 100,000 soldiers of the National Revolutionary Army in a ceremony announcing the start of the Northern Expedition, the campaign to unify China once and for all by annihilating the Northern Warlords of the Beiyang Government (Fengtian Clique and Zhili clique.)
With superior training and organization, supplies from the Soviet Union and the German Empire, and support from the people against corrupt warlords, The First United Front of the KMT and the CCP went from Zhu River to the Yangtze river by crushing the main forces of Wu Peifu and Sun Chuanfang. Meanwhile, the NRA victories raised morale and thus in turn raised army size, from 100,000 to 250,000,
With the NRA having control of the land between the Pearl River and the Yangtze River, they consolidate that control in 1927 and prepare to invade north of the Yangtze River. On April 12th, 1927, with Sun Yat-sen still living, the Shanghai Massacre of 1927 never happens, thus never splitting up the First United Front as in OTL, and never starting the Chinese Civil War between the KMT and the CCP as in OTL.
Instead, this day marked the reopening of conflicts between the First United Front and the Northern Warlord states with the Battle of Nanjing, where the First United Front quickly advanced through Nanjing, and the KMT made its capital in the city, thus starting the Nanjing decade. With the Shanghai purge never happening, the Northern Warlord states do not launch a counterattack, instead they build up defenses in the cities of Wuhan and Chonqing with secret Japanese support, who fear that the First United Front is too strong and may actually unite China.
The year of 1927 is thus dominated by the Yangtze River Campaign, whose major battles are the First Battle of Shanghai, the First Battle of Nanjing, The First Battle of Wuhan, and The First Battle of Chongqing. These four battles spanned out the entire year, each were extremely costly to both sides. Eventually, however, due to the superior training and organization, supplies from the Soviet Union and the German Empire, support from the people, and the guidance and inspiration of the great Dr. Sun Yat-sen The First United Front conquers all four cities by the end of the year, all of which are heavily damaged. Not only are the four cities damaged, however, but the KMT is too. Extremely heavy losses were inflicted on both sides, and those who served (especially those who died in the Yangtze River campaign) will forever be remembered as heroes of China.
The majority of this year is spent rebuilding the four cities of Shanghai, Nanjing, Wuhan, and Chongqing as well as building up the NRA in general, as a result of catastrophic losses. For eight months the 1928 Rebuildment of the First United Front occurs, for two months the Preparation of the Invasion of Beijing occurs. The remaining two months are spent during the Invasion of Beijing, which occurs in two stages, the Invasion of the land between Shanghai and the three other cities and the conquest of Beijing proper. With the conquest of Beijing completed in December of 1928, the Beijing Government falls, and thus the reunification of China under the First United Front of the KMT and the CCP is celebrated throughout the nation. With China reunified under the First United Front, Sun Yat-sen dies a satisfied, happy, and peaceful death.
Before dying, however, he writes the Three Principals of China. "As I have created the Three Principals of the People, my final work shall be the Three Principals of China. 1)Maintain the Three Principals of the People, at all times. 2) Be weary of both external threats such as the Japanese Empire 'and internal threats such as corruption from within. 3) Never break the First United Front between the Kuomintang and the Communist Party of China. If China is ever to survive, this sacred unity must never be broken." -Dr. Sun Yat-sen.
With the death of Dr. Sun Yat-sen, all of China mourns the loss of their great leader, "The Father of the Nation" and the "Forerunner of the Democratic Revolution." A grand parade in the capital of Nanjing is held for Dr. Sun Yat in his honor. While the Chinese people are unified in their mourning for Dr. Sun Yat-sen for now, what the year 1929 will bring is uncertain.
One month after the death of Sun Yat-sen's death, it was the new year, the year of 1929. Celebration was over, and so was unity in the KMT. During the Northern Expedition, Chiang allied with the Southern Warlords (including Yan Xinshan, Feng Yuxiang, Li Zongren, Bai Chongxi, and Fu Zuoyi). With the Northern Expedition being over, however, tensions between the KMT and the Gaunxi Clique erupt, with minor rebellions occurring sporadically and the Anti-Chiang Faction being declared.
Meanwhile, Muslim rebellions in Gansu occurred, thus destabilizing the KMT. With the destabilization of the Kuomintang, Chiang Kai-sek and his faction meets up with Mao Zedong and his faction to discuss how to counter this destabilization, and they reach an agreement to prepare during this year in 1929 and then launch the Anti-Destabilization Campaign militarily next year in 1930.