Short answers, pulled from the story.
The National Revolutionary Army officially formed in 1924 as the Kuomintang's military arm under Sun Yat-sen's leadership. Whampoa Military Academy opened that same year to train officer corps loyal to the party with Chiang Kai-shek serving as its first commandant.
The Northern Expedition began in July 1926 with Generalissimo Chiang Kai-shek leading the charge northward from Canton to defeat warlords like Wu Peifu and Sun Chuanfang. The campaign officially ended in December 1928 when Northeast China accepted Nationalist rule marking the nominal end of the Warlord Era.
The National Revolutionary Army suffered enormous losses including an estimated 750,000 combat casualties throughout the Second Sino-Japanese War. Between 1937 and 1945 approximately 14 million men were conscripted into service while actual active division numbers remained significantly lower than nominal strength figures.
Foreign aid improved capabilities starting from 1938 with Soviet support under the Sino-Soviet Non-Aggression Pact. From 1941 the United States became chief backer via Lend-Lease though strained relationships persisted between General Chiang and American commanders.
In regular provincial divisions standard-issue rifle was Hanyang 88 a Chinese-produced variant of German Gewehr 88. Central Government divisions typically equipped with Chiang Kai-shek rifle and other Mauser-pattern rifles imported from Germany Belgium Czechoslovak Republic.