'Swithin' was the Chinese and US advance to the south from Ledo in the northern part of Japanese-occupied Burma (1944).
Under the overall command of Lieutenant General Joseph W. Stilwell, these forces initially comprised the two US-equipped Chinese infantry divisions and one Chinese-manned armoured battalion with M3 light tanks of General Wei Li-huang’s Chinese Army in India, and Brigadier General Frank D. Merrill’s 5307th Composite Unit (Provisional), the US long-range penetration brigade generally known as 'Merrill’s Marauders'.
In October 1943 Lieutenant General Sun Li-jen’s Chinese 38th Division, which with the Chinese New 22nd Division and Chinese New 30th Division was the primary formation of the Chinese Army in India, began the advance to the south from Ledo toward Myitkyina and Mogaung while US engineers and Indian labourers extended the Ledo Road behind them. Lieutenant General Sinichi Tanaka’s 18th Division, part of Lieutenant General Masaki Honda’s two-division 33rd Army, was repeatedly outflanked by 'Merrill’s Marauders' and threatened with encirclement.
In 'Thursday' the Chindit forces of Major General O. C. Wingate’s Indian 3rd Division were to support the advance of the Chinese and US forces by interdicting the Japanese supply lines in the region of Indaw, which lies on the Irrawaddy river and also on the rail line and both extent to Myitkyina. One of Wingate’s brigades began marching across the Patkai mountains on 5 February 1944, and at a time early in March 1944 three other brigades were flown into landing zones behind the Japanese lines by Colonel Philip G. Cochran’s 1st Air Commando Group of Major General Howard C. Davidson’s 10th AAF, and established roadblocks and defensive strongholds around Indaw. On 24 March Wingate was killed in an air crash and succeeded by Brigadier W. D. A. Lentaigne, and on 17 May control of the Chindits passed from Lieutenant General W. J. Slim’s British 14th Army to Stilwell’s Northern Combat Area Command.
The Chindits now moved from the Japanese rear areas to new bases closer to Stilwell’s front, and were given additional tasks for which they were not equipped. They achieved several objectives, but only at the cost of exceptionally heavy losses. By the end of June, the Chindits had joined forces with the NCAC but were exhausted and withdrawn to India. Also on 17 May in a daring move aided by the Chindits of Brigadier J. M. Calvert’s Indian 77th Brigade, 'Merrill’s Marauders' captured the all-important airfield at Myitkyina. The Allies did not immediately exploit this success, and the Japanese were able to reinforce the town, which fell only after a siege lasting to 3 August. The airfield had nevertheless already become a vital link in the air supply route over the 'Hump'.
Farther to the east, the Chinese forces on the Yunnan front had launched an offensive starting in the second half of April, nearly 40,000 Chinese troops crossing the Salween river on a front of about 185 miles (300 km). Within a few days some 12 Chinese divisions, totalling 72,000 men, were attacking Lieutenant General Yuzo Matsuyama’s 56th Division, the other major component of the 33rd Army.
The Japanese forces in northern Burma were now fighting on two fronts: the Western Allies advancing from the north-west and the Chinese Nationalists from the north-east. The Chinese forces' Yunnan offensive was hampered by the monsoon rains and lack of air support, but succeeded in annihilating the garrison of Tengchung at the end of May. After overcoming determined Japanese resistance, in which the Japanese were helped by their fortuitous obtaining of the Chinese plans and codes, the Chinese captured Lungling at the end of August. At this point, the Japanese moved reinforcements (amounting to a further division in strength) to Yunnan and counterattacked, temporarily halting the Chinese advance.
The Allies launched a series of offensive operations into Burma during late 1944 and the first half of 1945. The command on the front was rearranged in November 1944. General Sir George Giffard’s British 11th Army Group was replaced by Lieutenant General Sir Oliver Leese’s Allied Land Forces South-East Asia, and the Northern Combat Area Command and Lieutenant General Sir Philip Christison’s Indian XV Corps, in the Arakan region, were placed directly under this new headquarters. Although the Allies were still attempting to complete the Ledo Road, it was apparent that it would not materially affect the course of the war in China.
The Japanese also made major changes in their command. The most important was the replacement of General Masamitsu Kawabe at the head of the Burma Area Army by General Heitaro Kimura, who threw the Allied plans into confusion by refusing to fight on the line of the Chindwin river and, recognising that most of his formations were weak and short of equipment, withdrew the bulk of his forces behind the line of the Irrawaddy river.
The Northern Combat Area Command resumed its temporarily paused advance at a time late in 1944, although it was progressively weakened by the return of Chinese troops, and the transport aircraft which supported them, to the main front in China. On 10 December 1944, Major General F. W. Festing’s British 36th Division on Northern Combat Area Command’s right flank made contact with units of the 14th Army near Indaw in northern Burma, and five days later Chinese troops on the Northern Combat Area Command’s left flank captured Bhamo. The Northern Combat Area Command made contact with the Yunnan armies on 21 January 1945, and the Ledo Road could finally be completed, although by this point in the war its value was uncertain.
Chiang Kai-shek ordered Lieutenant General David I. Sultan, now commanding the Northern Combat Area Command (Brigadier General J. P. Willey’s 'Mars' Task Force, Sun Li-jen’s two-division Chinese New 1st Army and Lieutenant General Liao Yueh-shang’s three-division Chinese New 6th Army) to halt his advance at Lashio, which was captured on 7 March. The Japanese were now focused on the war in central Burma, and now abandoned the northern front.
The Northern Combat Area Command’s operations ceased on 1 April, and its units returned to China and India, whereupon a US-led guerrilla force, OSS Detachment 101, took over the remaining military responsibilities of the Northern Combat Area Command.