Imphal offensive

Imphal offensive (see Map 50). This was the turning-point of the Burma campaign when, in March 1944, Mutaguchi's Fifteenth Japanese Army attacked from Burma into India. Mutaguchi's primary objective was to pre-empt an offensive by Slim's Fourteenth Army by destroying Slim's supply bases at Imphal. But Mutaguchi also wanted to gain a foothold for his Indian National Army (INA), hoping to precipitate a revolt in India. To make the British commit their reserves before launching this offensive, Lt-General Kawabe Masakazu (1886–1965), the Japanese Burma Area Army commander, struck into the Arakan in February 1944, precipitating the battle of the Admin Box.

Outnumbered, out-gunned, and without air superiority, Mutaguchi's offensive relied on speed and tactical surprise. It was a desperate gamble which nearly paid off. For though Slim was expecting, indeed hoping for, a Japanese offensive as a necessary preliminary to advancing himself—and had planned a withdrawal to the Imphal plain to fight on ground of his own choosing if one came—Mutaguchi still achieved tactical surprise because Slim had miscalculated the timing of the offensive and its strength.

To draw Slim's reserves away from the objectives of his other two Japanese divisions, Mutaguchi had his 33rd Division strike first, from the south, on 7 March. Part of this nearly trapped Slim's 17th Division at Tiddim, forcing it into a fighting retreat, while another part, Yamamoto Force, fought to destroy the 20th Division around Tamu but was eventually stopped at Shenam Saddle. A week later Mutaguchi's 15th Division, which attacked in the centre, and his 31st Division, which formed the northern part of the Japanese pincer, poured across the River Chindwin. But the Japanese Arakan offensive had been launched, and defeated, too quickly and this allowed two of Slim's divisions (5th and 7th) to be airlifted from there to Imphal. As the first men began landing on 19 March the Japanese were only 48 km. (30 mi.) away.

Slim had made another miscalculation, too. He had expected an assault on Kohima, to the north-west of Imphal, because its capture would sever Imphal's supply route from Dimapur, his main supply base. But he had estimated that the terrain was too difficult for the commander of the 31st Division, Lt-General Satō Kotuku, to deploy more than one regiment; in fact, Satō brought forward his whole division. After a bloody curtain-raiser with the 50th Indian Parachute Brigade at Sangshak the division's infantry group reached Kohima on 3 April.

Nine days later Mutaguchi's 15th Division cut the Kohima–Imphal road at Kangpokpi. Soon it was overlooking the defensive positions of Slim's 4th Corps and was only 10 km. (6 mi.) from them. But the Japanese were exhausted from road-building. They also lacked the necessary firepower and were defenceless against Slim's tanks, which the divisional commander had been told not to expect; in the desperate fighting which followed, Slim's 5th and 23rd Divisions gradually broke this Japanese stranglehold. But with his supply road cut, Slim had to start being supplied by air, an extraordinary achievement by the RAF's Third Tactical Air Force which, during the course of the four-month battle, moved prodigious amounts of men and supplies, including over 4.5 million litres of petrol (one million gallons), 12,000 reinforcements, 13,000 casualties, and 6.35 million kg. (14 million lb.) of rations.

Mutaguchi'slogistics were even more dire. He knew that insufficient supplies could be brought forward through the jungle and he had gambled on capturing Imphal quickly to obtain what he needed from the British supply dumps there. So when the town's defences held, and both the 17th and 20th Divisions escaped destruction, Mutaguchi decided to exceed his orders by striking at Dimapur which contained everything he needed. But this plan was thwarted by the cautious Kawabe and as Slim slowly stabilized the battle front during April and May, so Mutaguchi's situation became more and more desperate. His men—though not the INA—fought with great bravery. But Satō's withdrawal, against orders, from Kohima on 31 May, and his earlier refusal, or inability, to detach part of his division to aid 15th Division's attack on Imphal, undermined the whole offensive. Meanwhile the arrival of monsoon weather in mid-May, as well as disease and malnutrition, hampered Mutaguchi's force's movements and reduced their numbers. Slowly the battle turned in Slim's favour, the Dimapur–Imphal supply road was reopened on 22 June, and on 18 July Kawabe and Mutaguchi agreed that no further offensive operations were possible. Mutaguchi withdrew across the Chindwin, but Slim's forces followed on his heels and the withdrawal became a rout.

Imphal was an unmitigated disaster for the Japanese. Out of 85,000 fighting men, 53,000 became casualties (the British had 17,000), including 30,000 killed, while hundreds more died of disease, malnutrition, and exhaustion. Not one tank or heavy weapon was saved, and 17,000 mules and pack ponies perished. The Japanese in Burma never recovered and the INA never achieved the foothold in India it so desperately sought.

Bibliography

Evans, G., and and Brett-James, A. , Imphal (London, 1962).