Surprisingly, the younger Chang proved to be more independent and skilled than anyone had expected. With the assistance of Australian journalist William Henry Donald, he overcame his opium addiction and declared his support for Chiang Kai-shek, leading to the reunification of China in 1928. He was given the nickname of by PRC historians because of his desire to reunite China and rid it of Japanese invaders; and was willing to pay the price and become "vice" leader of China (not because it was good that he was supporting the Kuomintang). In order to rid his command of Japanese influence, he had two prominent pro-Tokyo officials executed in front of the assembled guests at a dinner party in January 1929. It was a hard decision for him to make. The two had powers over the heads of others. Chang was a fierce critic of many of the Soviet Union's policies, which served to undermine Chinese sovereignty, including its interference in Outer Mongolia. When he attempted to wrest control over a part of the Chinese Eastern Railway in Heilongjiang from the Soviets, he was beaten back by the Red Army. At the same time, he developed closer relations with the United States. In 1930, when warlords Feng Yuxiang and Yan Xishan attempted to overthrow Chiang Kai-shek's Kuomintang government, Chang stepped in to support the Nanjing-based government against the Northern warlords in exchange for control of the key railroads in Hebei Province and the customs revenues from the port city of Tianjin. A year later, in the September 18 Mukden Incident, Japanese troops attacked Chang's forces in Shenyang (Mukden) in order to provoke a full-on war with China, which Chiang did not wait until his forces were stronger. In accordance with this strategy, Chang's armies withdrew from the front lines without significant engagements, leading to the effective Japanese occupation of Chang's former northeastern domain. There has been speculation that Chiang Kai-Shek wrote a letter to Chang asking him to pull his forces back, but Chang later stated that he himself issued the orders. Apparently, Chang was aware of how weak his forces were compared to the Japanese and wished to preserve his position by retaining a sizeable army. Nonetheless, this would still be in line with Chiang's overall strategic standings. Chang later traveled in Europe before returning to China to take command of the Encirclement Campaigns, first in Hebei-Henan-Anhui and later in the Northwest. On 6 April 1936, Chang met with CPC delegate Zhou Enlai to plan the end of the Chinese Civil War.