In my view the best way to prevent the CCP resurgence after World War II would have been to evict the Soviet Red Army from Manchuria as soon as possible. On 14 August 1945 the USSR and KMT China signed a Treaty of Friendship and Alliance against Japan. The exchange of notes attached to this treaty had, among other things, the following two obligations:
(1) 'In accordance with the spirit of the above mentioned Treaty - that is, the Treaty of Friendship 'and Alliance between the Republic of China and the Union of Soviet Socialist Republics - and to implement its general idea and purposes, the Soviet Government agrees to render China moral support and assist her with military supplies and other material resources, it being understood that this support and assistance will go exclusively to the National Government as the Central Government of China.'
(2) 'During the negotiations on the ports of Dairen and Port Arthur and on the joint operation of the Chinese Changchun Railway, the Soviet Government regarded the Three Eastern Provinces - that is, Manchuria - as part of China and again affirmed its respect for the complete sovereignty of China over the Three Eastern Provinces and recognition of their territorial and administrative integrity.'
Prior to the treaty Stalin also went on record stating that Soviet forces would withdraw from Manchuria beginning three weeks after the surrender of Japan, to be completed within three months. However, the Soviets violated their promise to leave immediately and furthermore blocked KMT troops from entering into Manchuria either through seaports or by the single railway leading there from China proper. Rather than providing 'military and moral aid' to Chiang Kai Shek as stipulated under the above, the Soviets supported the Chinese communists.
At the 1068th Plenary Meeting of the United Nations on 1 December 1961, representative Tsiang (ROC) declared:
"Shortly after V-J Day, the Chinese communist forces under the command of Lin Piao infiltrated into Manchuria in large numbers, amounting to about 200,000 men. Let me remind the Assembly that this commander, Lin Piao, was the same man who led the so-called Chinese volunteers into Korea
[Bob note: actually Peng Teh-Huai]. All these 200,000 Chinese communist soldiers were then unarmed. A short time afterwards, these 200,000 men were all fully, armed with Japanese equipment and supplied with Japanese munitions. Since all the equipment and supplies of the Japanese forces in Manchuria were either captured by or surrendered to the Soviet forces, the Chinese communist forces at that time could have only one source of supply-namely, the Soviet Army. "
According to Tseng: "In the first month of the occupation of Manchuria, from 9 August to 9 September 1945, the Soviet Army captured from the Japanese army 594,000 prisoners of war, 925 aircraft, 369 tanks, 35 armoured cars, 1,226 pieces of field artillery, 4,836 machine guns, 300,000 rifles, 133 radio sets, 2,300 motor vehicles, 125 tractors, 17,497 horses and mules, and 742 depots with munitions and supplies included. In addition, at the time of its surrender, the Japanese Kwantung army had in storage in various parts of Manchuria 1,436 pieces of field artillery, 8,989 machine guns, 11,052 grenade-throwers, 3,078 trucks, 104,777 horses, 21,084 supply cars, 815 special vehicles, and 287 command cars.
These captured supplies and equipment were not transferred to the Chinese Government. Neither were the surrendered items."
According to
page 186 of "The China Handbook, 1950," Chinese forces under the central government collected the following weapons and equipment from Japanese troops in China, Taiwan, and northern FIC by mid-April 1946: 685,897 rifles, 60,377 pistols, 29,822 light and heavy machine guns, 12,446 artillery pieces "of various kinds and calibers," 383 tanks, 151 armored trucks, 15,785 trucks, 74,159 horses, 1,068 aircraft, and 1,400 naval vessels with total tonnage 54,600 (most of these were useless). Fuel and munitions captured amounted to 3,101,927 gallons of avgas, 6,000 tons of aerial bombs, ~180,994,000 rounds of rifle ammunition, ~2,035,000 rounds of pistol ammunition, and over 2,070,000 shells "of various kinds." Chinese communist troops occupied Chengteh, Chihfeng, Tulun, Kalgan, and Kupeikow, which were not handed over to the national army. (I do not know what became of this materiel, perhaps it was destroyed after being collected)
Therefore, the answer seems to apply pressure on the USSR to get out of Manchuria ASAP under the terms of the treaty rather than allow them to further foment civil war and communist revolution. Considering the threat, if all else failed the KMT may have been justified in issuing an ultimatum for the Soviets to either leave in accordance with the agreement or be treated as a hostile occupation force.