Why were the nationalists in china successful between 1928 and 1937

The Nationalist government from 1928 to 1937

The most-serious immediate problem facing the new government was the continuing military separatism. The government had no authority over the vast area of western China, and even regions in eastern China were under the rule of independent regimes that had lately been part of the Nationalist coalition. After an unsuccessful attempt at negotiations, Chiang launched a series of civil wars against his former allies. By 1930 one militarist regime after another had been reduced to provincial proportions, and Nanjing’s influence was spreading. Explained in material terms, Chiang owed his success to the great financial resources of his base in Jiangsu and Zhejiang and to foreign arms. Quick recognition by the foreign powers brought the Nationalist government the revenues collected by the efficient Maritime Customs Service; when the powers granted China the right to fix its own tariff schedules, that revenue increased.

this is a good question! i'll do some research and come back when i have the answer!