Operation U-Go

The U Go offensive, or Operation C (ウ号作戦 U Gō sakusen), was the Japanese offensive launched in March 1944 against forces of the British Empire in the northeast Indian regions of Manipur and the Naga Hills (then administered as part of Assam). Aimed at the Brahmaputra Valley, through the two towns of Imphal and Kohima, the offensive along with the overlapping Ha Go offensive was one of the last major Japanese offensives during the Second World War. The offensive culminated in the Battles of Imphal and Kohima, where the Japanese and their allies were first held and then pushed back.

The under Lieutenant-General Motoso Yanagida would destroy the 17th Indian Infantry Division at Tiddim, then attack Imphal from the south.

33rd Infantry Division

Yamamoto Force, formed from units detached from the 33rd and 15th Divisions under Major-General (commander of 33rd Division's Infantry Group), supported by tanks and heavy artillery, would destroy the 20th Indian Infantry Division at Tamu, then attack Imphal from the east.

Tsunoru Yamamoto

The under Lieutenant-General Masafumi Yamauchi would envelop Imphal from the north.

15th Infantry Division

In a separate subsidiary operation, the under Lieutenant-General Kōtoku Satō would isolate Imphal by capturing Kohima, then push onwards to capture the vital Allied supply base at Dimapur in the Brahmaputra valley.

31st Infantry Division

The Allies were preparing to take the offensive themselves in early 1944. The Indian XV Corps was advancing in the coastal Arakan Province, while the British IV Corps had pushed two Indian infantry divisions almost to the Chindwin River at Tamu and Tiddim. These two divisions were widely separated and vulnerable to being isolated.

The Japanese planned that a division from the Twenty-Eighth Army would launch a diversionary attack in the Arakan, codenamed Ha Go, in the first week of February. This would attract Allied reserves from Assam, and also create the impression that the Japanese intended to attack Bengal through Chittagong.

In the centre, Mutaguchi's Fifteenth Army would launch the main attack into Manipur in the first week in March, aiming to capture Imphal and Kohima, scattering British forces and forestalling any offensive movements against Burma.^[12]^[13] In detail, the Fifteenth Army plans were:

At the insistence of Bose, two brigades from the Indian National Army were also assigned to the attacks on Imphal from the south and east. The Japanese had originally intended using the INA as auxiliaries to their forces only, for reconnaissance and propaganda.^[14]

The staff at Burma Area Army had originally thought this plan too risky. They believed it was unwise to separate the attacking forces so widely, but several officers who were vocal in their opposition were transferred.^[15] Mutaguchi's divisional commanders were also pessimistic. They thought that Mutaguchi was gambling too heavily on gaining early success to solve supply problems. Some of them thought him a "blockhead", or reckless.

Allied plans[edit]

In early 1944, the Allied formations in Assam and Arakan were part of the British Fourteenth Army, commanded by Lieutenant General William Slim. Over the preceding year, since the failure of an earlier offensive in the Arakan, he and his predecessor, General George Giffard, had been striving to improve the health, training and morale of the British and Indian units of the army. Through improvements in the lines of communication, better administration in the rear areas, and above all, better supply of fresh rations and medicines, these efforts had been successful. The Allies had also developed methods to counter the standard Japanese tactics of outflanking and isolating formations. In particular, they would increasingly depend upon aircraft to supply cut-off units. The Japanese had not anticipated this, and their attacks would be thwarted several times.

From various intelligence sources, Slim and Lieutenant General Geoffry Scoones (commanding Indian IV Corps) had learned of the general intentions of the Japanese to launch an offensive, although they did not have specific information on the Japanese objectives and were to be surprised several times when the Japanese did launch their attacks. Rather than anticipate the Japanese by attacking across the Chindwin, or trying to defend the line of the river itself, Slim intended to exploit known Japanese logistical weaknesses by withdrawing into Imphal to fight a defensive battle where the Japanese would be unable to supply their troops.^[16]

Impact[edit]

The Japanese defeats at Kohima and Imphal were the largest up until that time. The British and Indian forces had lost around 16,987 men, dead, missing and wounded.^[2] The Japanese suffered 60,643 casualties, including 13,376 dead.^[2] Most of these losses were the result of starvation, disease and exhaustion.

The defeat resulted in sweeping changes in command within the Japanese Army in Burma. Mutaguchi sacked all his division commanders during the operation, before being sacked himself on 30 August. Kawabe, whose health was broken, was also dismissed. Many of the senior staff officers at the headquarters of Fifteenth Army and Burma Area Army were also transferred to divisional or regimental commands.^[18]