Imphal and Kohima

Operation U-Go began on 8 March 1944, when the Japanese Fifteenth Army crossed the Chindwin and advanced toward the Allied base at Imphal. The offensive sought to isolate IV Corps, seize its supplies and cut the road between Imphal and Dimapur at Kohima. Japanese forces approached from several directions: the 33rd Division threatened the southern approaches, the 15th Division attacked from the north-east, and the 31st Division moved through the hills toward Kohima. Allied divisions had been spread across the frontier. The 17th Indian Division, cut off on the Tiddim road in mid-March, fought its way back to the Imphal plain, and on 29 March Japanese troops cut the Imphal–Kohima road, isolating IV Corps.

The fighting at Kohima became a siege in early April. The Japanese 31st Division surrounded the town and captured positions on the ridge, while the garrison, commanded by Hugh Richards, held a small defensive perimeter. Japanese attacks also closed around Imphal, where IV Corps defended the plain and its approaches. Allied troops relied on air supply while reinforcements moved toward the threatened positions. The British 2nd Division and XXXIII Corps reached the Dimapur area, and troops broke the roadblock at Zubza on 14 April. On 18 April the 161st Indian Brigade, backed by the 2nd Division's guns and tanks, broke through to the garrison, and the 2nd Division took over the defence of Kohima two days later.

Allied counter-attacks then pushed Japanese forces from the Kohima ridge and reopened sections of the road. At Imphal, Indian divisions held the defensive perimeter and counter-attacked at key approaches, including Nungshigum. The 5th Indian Division had been flown in from the Arakan, while RAF aircraft carried supplies and personnel to the besieged forces. Japanese formations faced increasingly severe shortages of food and ammunition. The Kohima ridge was cleared by 13 May, and on 31 May Lieutenant General Kōtoku Satō ordered his 31st Division to withdraw from Kohima, though fighting continued as Allied forces cleared the road south.

On 22 June, troops advancing from Kohima and Imphal met at Milestone 109, ending the siege of Imphal and reopening the road. The Allies continued to pursue the retreating Japanese, with operations extending toward the Chindwin during July. The campaign ended on 3 July. Allied losses were reported as about 12,500 at Imphal and 4,000 at Kohima, while the BBC account gave fewer than 17,000 British losses for the campaign. Japanese losses were reported in different ways: 53,000 dead and missing for the Fifteenth Army, and 54,879 killed and wounded for the Battle of Imphal. These figures used different measures and were not treated here as directly additive.