(BNA) with Ne Win as its commander on 1 August 1943 when Burma received nominal independence. In late 1944, it had a strength of approximately 15,000. Disillusioned by the Japanese occupation, the BNA realigned with the Allies on 27 March 1945. Thai occupation of Kengtung and Mong Pan In 1942, the Imperial Japanese Army invaded the Federated Shan States from Thailand. The Japanese forces with superior air power went on to dislodge the Nationalist Chinese forces, who had been invited by the British for the region's defence, by November 1942. The Thai Phayap Army accompanied the Japanese forces on the invasion, including that of Kengtung in May 1942. The IJA allowed the Phayap Army to occupy Kengtung and parts of Mongpan state. Following the existing agreement between Thai Prime Minister Plaek Phibunsongkhram (Phibun) and the Japanese Empire, on 18 August 1943, the Japanese government agreed to the Thai annexation of Kengtung and Mongpan states (as well as the annexation of Kelantan, Trengganu, Kedah, Perlis states and nearby islands in Malaya.) The Thai government wanted the Karenni states and remaining southern Shan states but the Japanese assigned them to their client State of Burma in September 1943. The Thai army would remain there until the end of the war although the Thai government began to alter its position when the tide of war began to favour the allies. After the Phibun government fell in August 1944, the new government of Khuang Aphaiwong communicated to the British government it renounced all claims to the Shan states and northern Malaya, and that it would immediately return the territories to Britain. The Churchill government did not accept the Thai overture, and was prepared to retaliate. The Thai army evacuated the two Shan states only in August 1945. Modern era Chinese Nationalist incursion Soon after gaining independence, the central government led by U Nu faced several armed rebellions. The most serious was the Chinese Nationalist KMT invasion of Shan State in 1950. Driven out by the Chinese Communist forces, Nationalist KMT troops (about 16,000 at the peak) planned to use the region east of the Salween river as a base from which to regain their homeland. In March 1953, the KMT forces with US assistance were on the verge of taking the entire Shan State, and within a day's march of the state capital Taunggyi. The Burmese army drove back the invaders east across the