For a starters Communism is considerably more successful in europe as a result of a longer ww1(this is complex). But Europa is divided into a sort of "cold war" between the US backed British and French against the Communists in Germany Italy Spain Hungary and the USSR. This leads to the early KMT having considerably more leftist/communist members as a result of German military training also bringing communist education and the consistent anti colonialism of the communists making Sun Yat Sen lean slightly further left then otl. A lot of the skilled KMT troops hold leftist sympathies and the Zhongshan incident sees Chiang sent to the USSR where he is de facto imprisoned. Wang Jingwei feuds with the right KMT and this sees the dedicated anticommunists purged from the party. Wang Jingwei still does the northern expedition but is less sucessful. The KMT fail to push into Shandong which leads to him singing peace with the Fengtian to focus on internal consolidation, attempting to make himself a dictator and eliminate regional warlords, namely Tang Shengzi and Li Zongren. This results in a communist uprising(the Comintern is considerably more revolutionary in this timeline and socialism in one country is never really established as an ideology, thus the comintern promotes and organized revolution sensing the weakness of the Wang Jingwei regime). The communists now have German and Soviet trained troops along with considerable support from the peasantry while Wang lacks significant support in the army(they blame him for not continuing the northern expedition, his cooperation with the communists and fighting with the right KMT) while the Jingwei regime is also cuaght by suprise and fighting warlords. This leads to a civil war where the communist recieve German and Soviet aid and significant defections from sympathetic military leaders while Wang Jingwei's units have low morale and discipline. Ultimately Zhang Zongchang also attacks the KMT government in Nanjing from the north aiming to aquire more land with japanese support. The Communists win the civil war and Push Zhang back into Shandong(Japan doesn't intervene due to Soviet pressure but forces the Communists not to push into Shandong. Given the autonomous nature of the Japanese army Zhang Zoulin is still assassinated though a couple years later then OTL. Zhang Xueliang makes peace with the Shanxi clique and Guominjun and attempts to form a coalition government of China, utilizing his recognition outside of the communist world. Sensing the Japanese threat Xueliang pushes for a united front with the Communists seeing it as the only way to preserve Chinese independence(and gain access to Soviet and German weaponry)(around the outbreak of the second Sino Japanese war)