Mao's Communist forces mobilized the peasantry in rural China against the Japanese, and at the time of the Japanese surrender in 1945 the Chinese Communist Party had built an army of nearly a million soldiers. The pressure Mao's forces placed on the Japanese benefitted the Soviet Union, and thus the CCP forces were supplied by the Soviets. The ideological unity of the CCP, and the experience acquired in fighting the Japanese, prepared it for the next battles against the Kuomintang. Though Chiang's forces were well equipped by the US, they lacked effective leadership, political unity and experience. In January 1949, Chiang Kai-shek stepped down as leader of the KMT and was replaced by his vice-president, Li Zongren. Li and Mao entered into negotiations for peace, but Nationalist hardliners rejected Mao's demands. The Communist military capability was a deciding factor in resolving the impasse, and when Li sought an additional delay in mid-April 1949, the Chinese Red Army crossed the Yangtze (Chang) River. Chiang fled to the island of Formosa (Taiwan), where approximately 300,000 soldiers had already been airlifted. Over the course of 4 months beginning in August 1948, the ROC leaders relocated the Republic of China Air Force to Taiwan, taking over 80 flights and 3 ships. writes in his book on the subject that an average of 50 or 60 planes flew daily between Taiwan and China transporting fuel and ammunition between August 1948 and December 1949. Chiang also sent the 26 naval vessels of the Nationalist army to Taiwan. The final Communist assault against Nationalist forces began on and continued until the end of summer. By August, the People's Liberation Army dominated almost all of mainland China; the Nationalists held only Taiwan and the Pescadores Islands, Guangdong Province, and a few regions in China's far west. Institute of History and Philology director Fu Ssu-nien spearheaded a rush to persuade scholars to flee to Taiwan, as well as bringing books and documents. In 1948, Chiang Kai-shek began planning the KMT retreat to Taiwan with a plan to take gold and treasure from the mainland. The amount of gold that was moved differs according to sources, but it is usually estimated as between three million to five million taels (approximately 113.6-115.2 tons; one tael is 37.2 grams). Other than gold, KMT brought old relics, which are now kept in the National Palace Museum in Taipei, Taiwan.