The 'Battle of Kohima', together with the closely related and simultaneous 'Battle of Imphal', proved to be the turning point of the Japanese 'U' (ii) offensive from Burma into north-eastern India during 1944, and was an extremely sanguinary battle between Japanese and British forces in three stages round the town of Kohima, now the capital of Nagaland in north-eastern India (4 April/22 June 1944).

In the first stage, between 3 and 16 April, the Japanese attempted to capture Kohima ridge, a feature which dominated the road by which the besieged British and Indian troops of Lieutenant General G. A. P. Scoones’s Indian IV Corps at Imphal were supplied. In the second stage, by the middle of April, the initially small British and Indian force at Kohima was relieved. And in the third stage, from 18 April to 13 May, British and Indian reinforcements counterattacked to drive the Japanese from the positions they had captured. The Japanese abandoned the ridge at this point but continued to block the road linking Kohima and Imphal road. From 16 May to 22 June the British and Indian troops pursued the retreating Japanese and reopened the road. The battle ended on 22 June when British and Indian troops from Kohima in the north and Imphal in the south met at Milestone 109, ending the Japanese siege of Imphal.

The Japanese 'U' (ii) plan to invade India had initially been intended as a spoiling attack against the British IV Corps at Imphal in Manipur, to disrupt the Allied offensive plans for that year. The commander of the Japanese 15^th Army, Lieutenant General Renya Mutaguchi, then enlarged the plan to provide for an invasion of India itself and perhaps even the overthrow the British Raj.

Mutaguchi’s thinking was that if the Japanese could win a strong foothold in India they would thereby demonstrate the weakness of the British empire and provide encouragement to Indian nationalists in their decolonisation efforts. Moreover, occupation of the area around Imphal would exercise a severe and adverse effect on US efforts to supply Generalissimo Chiang Kai-shek’s Chinese Nationalist army. Mutaguchi and his advocates eventually overcame the objections of the staffs of various Japanese headquarters, and the offensive was approved by the Imperial General Headquarters on 7 January 1944.

Part of the plan involved sending Lieutenant General Kotoku Sato’s 31^st Division (58^th Regiment, 124^th Regiment, 138^th Regiment and 31^st Mountain Artillery Regiment) to capture Kohima and thus cut off Imphal from overland supply. Mutaguchi wished to exploit the capture of Kohima by pushing the 31^st Division on to Dimapur, the vital railhead and logistic base in the Brahmaputra river valley.

Sato was unhappy with his role. He had not been involved in the planning of the offensive, and had grave misgivings about its chances. He had already told his staff that they might all starve to death and, in common with many other senior Japanese officers, considered Mutaguchi to be a 'blockhead'. He and Mutaguchi had also been on opposite sides during the split between the Toseiha and Kodoha factions within the Imperial Japanese army during the early 1930s, and Sato believed he had reason to distrust Mutaguchi’s motives.

Starting on 15 March 1944, the 31^st Division crossed the Chindwin river near Homalin and moved to the north-west along jungle trails on a front almost 60 miles (100 km) wide. Because of a shortage of transport, half the artillery regiment’s mountain guns and the infantry regiments' heavy weapons were left behind, and supplies of food and ammunition sufficient for only three week were carried. Although the march was difficult, good progress was made. The left wing of the division, based on the bulk of the 58^th Regiment and commanded by the division’s Infantry group commander, Major General Shigesaburō Miyazaki, was ahead of the neighbouring formation, Lieutenant General Masafumi Yamauchi’s 5^th Division on the right of the thrust toward Imphal, when they clashed with Indian troops covering the northern approaches to Imphal on 20 March.

The Indian troops at Sangshak were those of Brigadier M. Hope-Thomson’s Indian 50^th Parachute Brigade. Although the brigade was not Miyazaki’s objective, he decided to clear it from his line of advance. The resulting 'Battle of Sangshak' continued for six days. The parachute brigade’s troops were desperately short of drinking water, but Miyazaki was handicapped by lack of artillery until near the end of the battle. Eventually, as some of the 15^th Division's troops joined the battle, Hope-Thomson withdrew. The Indian 50^th Parachute Brigade lost 600 men, while the Japanese had suffered more than 400 casualties. Miyazaki had also captured some of the food and munitions that had been dropped by aircraft of the Royal Air Force to the defenders of Sangshak. Despite this minor success, Miyazaki’s force, which had shortest and easiest route to Kohima, was delayed by an invaluable week.

Meanwhile, the commander of the British 14^th Army, Lieutenant General W. J. Slim, belatedly realised (in part from Japanese documents captured at Sangshak) that an entire Japanese division was advancing on Kohima. Slim and his staff had originally believed that the area’s forbidding terrain would prevent the Japanese from sending anything larer thsan one regiment against Kohima. Slim knew that there were few fighting troops, as opposed to soldiers in line-of-communication units and supporting services, in Kohima and none at all at the vital base of Dimapur 30 miles (48 km) to the north. Dimapur contained an area of supply dumps 11 miles (18 km) long and 1 mile (1.6 km) wide. As the fall of Dimapur would have been disastrous for the Allies, Slim asked his superior, General Sir George Giffard, the commander of the 11^th Army Group, for more troops to protect Dimapur and to prepare to relieve Imphal.

The Allies were already hastily reinforcing the Imphal front. As part of this move, the infantry and artillery of Major General H. R. Briggs’s Indian 5^th Division were flown from the Arakan western coastal region of Burma, where the division had just participated in the defeat of the Japanese 'Ha' subsidiary offensive in the 'Battle of the Admin Box'. While the main body of the division went to Imphal, around which some units had already been isolated and almost all of the IV Corps' reserves had already been committed, Brigadier D. Warren;s Indian 161^st Brigade and the Indian 24^th Mountain Artillery Regiment were flown to Dimapur.

At a time early in March, Brigadier L. E. C. M. Perown’s 23^rd Long-Range Penetration Brigade was removed from Major General O. C. Wingate’s 'Chindit' force and despatched by rail from the area of Lalaghat to Jorhat, 50 miles (80 km) to the north of Dimapur, from which it could threaten the flank of any Japanese attack on the base. Giffard and General Sir Claude Auchinleck, the commander-in-chief of the British Indian Army, also prepared to send Major General J. M. L. Grover’s British 2^nd Division and the headquarters of Lieutenant General M. G. M. Stopford’s Indian XXXIII Corps from reserve in southern and central India to Dimapur, by road and rail. Until the XXXIII Corps' headquarters could arrive at Dimapur, the headquarters of Major General R. P. L. Ranking’s No. 202 Line of Communication Area took command of the area.

Kohima’s strategic importance in Japan’s wider 1944 Chindwin offensive lay in the fact that it was the summit of a pass offering the Japanese the best route from Burma into India. Through it ran the road which was the main supply route between the base area at Dimapur in the Brahmaputra river valley and Imphal, where the British and Indian troops of the IV Corps (Indian 17^th, 20^th and 23^rd Divisions) faced the main Japanese offensive.

Kohima ridge itself extends approximately north and south. The road from Dimapur to Imphal climbs to its northern end and runs along its eastern face. In 1944, Kohima was the administrative centre of Nagaland, and the resident deputy commissioner was Charles Pawsey, whose bungalow stood on the hillside at a bend in the road, with its gardens and tennis court, and a clubhouse, on terraces above. Although some terraces around the village had been cleared for cultivation, the steep slopes of the ridge were densely forested. To the north of the ridge lay the densely inhabited area of Naga Village, crowned by Treasury Hill and Church Knoll: Baptist and other Christian missionaries had been active in Nagaland over the preceding 50 years or so. To the south and west of Kohima Ridge were GPT Ridge and the jungle-covered Aradura Spur. The various British and Indian service troop encampments in the area gave their names to the features which were to be important in the battle: thus the Field Supply Depot became FSD Hill or merely FSD. The Japanese later assigned their own codenames to the features: for example, Garrison Hill, which overlooked Kohima, became known as Inu (dog) and Kuki Piquet as Saru (monkey).

Before the Indian 161^st Brigade arrived, the only fighting troops in the Kohima area were the newly raised 1/Assam Regiment and a few platoons of the 3^rd (Naga Hills) Battalion of the paramilitary Assam Rifles. Late in March Indian 161^st Brigade deployed in Kohima, but Ranking ordered them back to Dimapur as it was felt initially that Dimapur had more strategic importance. Kohima was regarded as a roadblock, while Dimapur was the railhead where the majority of Allied supplies arrived and were stored. Slim also feared that the Japanese might leave only a detachment to contain the garrison of Kohima while the main body of the 31^st Division moved along tracks to the east to attack Dimapur. To Slim’s relief, Sato concentrated on capturing Kohima. (Early in the siege, on 8 April, Mutaguchi issued a direct order to Sato to send a detachment to advance on Dimapur. Sato unwillingly despatched a battalion of the 138^th Regiment, but a few hours later Mutaguchi’s superior, Lieutenant General Masakasu Kawabe, commander of the Burma Area Army, vetoed the move.)

As the right wing and centre of the 31^st Division approached Jessami, 30 miles (48 km) to the east of Kohima, from 1 April elements of the Assam Regiment fought delaying actions against them. Nevertheless, the men in the forward positions were soon overrun and the Assam Regiment was ordered to withdraw. By the night of 3 April, Miyazaki’s troops had reached the outskirts of the Naga Village and begun to probe into Kohima from the south.

The headquarters of Stopford’s XXXIII Corps assumed responsibility for the front from Ranking’s No. 202 Line of Communication Area on 3 April, and on the following dat Stopford ordered the Indian 161^st Brigade to move forward to Kohima once again, but only the 4/Queen’s Own Royal West Kent Regiment, commanded by Lieutenant Colonel John Laverty, and one company of the 4/7^th Rajput Regiment had reached Kohima before the Japanese cut the road to the west of the ridge. Besides these troops of the Indian 161^st Brigade, the garrison comprised one raw battalion (the Shere Regiment) of the Royal Nepalese army, some companies of the Burma Regiment, some units of the Assam Regiment which had retired to Kohima, and various detachments of convalescents and line-of-communication troops. The garrison numbered about 2,500 me, of whom about 1,000 were non-combatants, and was commanded by Colonel Hugh Richards, who had served formerly with the 'Chindits'.

The siege of Kohima began on 6 April. The garrison was continually shelled and mortared, in many instances by Japanese using weapons and ammunition captured at Sangshak and from other depots, and was slowly compressed into a small perimeter on Garrison Hill. The British and Indian forces had artillery support from the main body of the Indian 161^st Brigade, which was itself cut off 2 miles (3.2 km) away at Jotsoma. As at Sangshak, they were very short of drinking water: the water supply point was on GPT Ridge, which was captured by the Japanese on the first day of the siege. Some of its defenders were unable to retreat to other positions on the ridge and instead withdrew toward Dimapur. Canvas water tanks on FSD and at the Indian General Hospital had neither been filled nor dug in to protect them from fire. A small spring was discovered on the northern side of Garrison Hill, but this could be reached only at night. The medical dressing stations were exposed to Japanese fire, and wounded men were often hit again as they waited for treatment.

Some of the heaviest fighting took place at the northern end of Kohima Ridge, around the deputy commissioner’s bungalow and tennis court, in what became known as the 'Battle of the Tennis Court'. The tennis court itself became a no-man’s land, with the Japanese and the defenders of Kohima dug in on opposite sides, so close to each other that grenades were thrown between the trenches.

On the night of 17/18 April, the Japanese finally captured the area of the DC’s bungalow. Other Japanese captured Kuki Picquet, cutting the garrison in two. The defenders' situation was desperate, but the Japanese did not follow by attacking Garrison Hill as by now they were exhausted by hunger and the fighting, and when daylight broke, troops of the Indian 161^st Brigade arrived to relieve the garrison.

Grover’s British 2^nd Division had begun to arrive at Dimapur early in April. By 11 April, the 14^th Army had about the same number of troops in the area as the Japanese. Brigadier V. F, S. Hawkins’s British 5^th Brigade of the 2^nd Division broke through Japanese roadblocks to relieve the Indian 161^st Brigade in Jotsoma on 15 April. Brigadier W. G. Smith’s British 6^th Brigade took over the Indian 161^st Brigade’s defensive position (the 'Jotsoma Box'), allowing the Indian 161^st Brigade with air, artillery and armour support to launch an attack toward Kohima on 18 April. After a day’s heavy fighting, the brigade’s leading troops, the 1/1^st Punjab Regiment, broke through and started to relieve the Kohima garrison. By this point, Kohima resembled a World War I battlefield with smashed trees, ruined buildings and the ground covered in craters.

Under cover of darkness, some 300 wounded men were brought out under fire. Although contact had been established, it took a further 24 hours to secure the road between Jotsoma and Kohima. During 19 April and into the early hours of 20 April, the British 6^th Brigade replaced the original garrison, and at 06.00 on 20 April, Richards handed over responsibility for the garrison. 6^th Brigade observers were taken aback by the condition of the garrison, one battle-hardened officer commenting that 'They looked like aged, bloodstained scarecrows, dropping with fatigue; the only clean thing about them was their weapons, and they smelt of blood, sweat and death.'

Miyazaki continued his efforts to take Garrison Hill, and there was heavy fighting for this position for several more nights, with high casualties on both sides. The Japanese positions on Kuki Picquet were only 50 yards (46 m) from Garrison Hill, and fighting was often hand-to-hand. On the other flank of Garrison Hill, during the night of 26/27 April, a British attack recaptured the clubhouse above the Deputy Commissioner’s bungalow, which overlooked most of the Japanese centre.

The Japanese now reorganised their forces for defence. Their Left Force under Miyazaki held Kohima Ridge with four battalions; the divisional headquarters under Sato and the Centre Force under Colonel Shiraishi held Naga Village with another four battalions; and the much smaller Right Force held the villages to the north and east.

To support their attack against the Japanese positions, the British had amassed 38 3.7-in (94-mm) mountain howitzers, 48 25=pdr gun/howitzers and two 5.5-in (139.7-mm) medium guns. The RAF, in the form primarily of Hawker Hurricane single-engined fighter-bombers of No. 34 Squadron and Vultee Vengeance single-engined dive-bombers of No. 84 Squadron, also bombed and strafed the Japanese positions. The Japanese could oppose them with only 17 light mountain guns, for which there was very little ammunition. Even so, the progress of the British counterattack was slow. Tanks could not easily be used, and the Japanese occupied bunkers which were very deeply dug in, well-concealed and mutually supporting.

While the British 6^th Brigade defended Garrison Hill, the other two brigades of the 2^nd Division tried to outflank both ends of the Japanese position, in Naga Village to the north and on GPT Ridge to the south. The monsoon had broken by this time, and the steep slopes were covered in mud, making movement and supply very difficult. In places Brigadier W. H. Goschen’s British 4^th Brigade had to cut steps up hillsides and build handrails in order to make progress. On 4 May, the British 5^th Brigade secured a foothold in the outskirts of Naga Village but lost it to a counterattack, and on the same day the British 4^th Brigade, having made a long flank march around Mt Pulebadze to approach Kohima Ridge from the south-west, attacked GPT Ridge in driving rain and captured part of the ridge by surprise but was unable to secure the entire ridge. Two successive commanders of British 4^th Brigade were killed in the subsequent close-range fighting on the ridge.

Both outflanking moves having failed because of the terrain and the weather, the British 2^nd Division concentrated on attacking the Japanese positions along Kohima Ridge from 4 May. Fire from Japanese positions on the reverse slope of GPT Ridge repeatedly caught British troops attacking Jail Hill in the flank, inflicting heavy casualties and preventing them from capturing the hill for a week. However, the various positions were slowly taken. Jail Hill, together with Kuki Picquet, FSD and DIS, was finally captured Brigadier F. J. Loftus-Tottenham’s Indian 33^rd Brigade on 11 May, after a barrage of smoke shells had blinded the Japanese machine-gunners and allowed the troops to secure the hill and dig in.

The last of the Japanese positions on the ridge to be captured were the tennis court and gardens above the Deputy Commissioner’s bungalow. On 13 May, after several failed attempts to outflank or storm the position, the British finally bulldozed a track to the summit above the position, up which a tank could be dragged. A Grant tank crashed down onto the tennis court and destroyed the Japanese trenches and bunkers there. The 2/Dorsetshire Regiment followed and captured the hillside where the bungalow formerly stood, thus completing the clearance of Kohima Ridge. The terrain had been reduced to a fly- and rat-infested wilderness, with half-buried human remains everywhere. The conditions under which the Japanese troops had lived and fought have been described by several sources as 'unspeakable'.

The situation for the Japanese worsened still further as yet more Allied reinforcements arrived. Major General F. W. Messervy’s Indian 7^th Division was arriving piecemeal by road and rail from the Arakan region. Its Indian 33^rd Brigade had already been released from XXXIII Corps reserve to join the fighting on Kohima Ridge on 4 May. The Indian 114^th Brigade and the divisional headquarters arrived on 12 May and, with the Indian 161^st Brigade under command, the division concentrated on recapturing Naga Village from the north. The independent India 268^th Brigade was used to relieve the brigades of the British 2^nd Division and allow them to rest before they resumed their drive southward along the riad to Imphal.

Nevertheless, when the Allies launched another attack on 16 May, the Japanese continued their tenacious defence of Naga Village and the Aradura Spur. An attack on Naga Hill on the night of 24/25 May gained no ground. Another attack, mounted against both ends of the Aradura Spur on the night of 28/29 May was even more decisively repulsed. The repeated setbacks, with exhaustion and the effects of the climate began to affect the morale of the British 2^nd Division especially.

The decisive factor in the Japanese defeat was their lack of supplies. The 31^st Division had embarked on the operation with food supplies sufficient for only three weeks, and once these supplies had been consumed, the Japanese had to exist on meagre captured stocks and what they could forage in increasingly hostile local villages. (Shortly before the siege of Kohima began, the Japanese had captured a huge warehouse in Naga Village with enough rice to feed the division 'for three years', but it was immediately bombed and the stock of rice was destroyed.) The British 23^rd Long-Range Penetration Brigade, which had been operating behind the Japanese division, cut the Japanese supply lines and prevented them foraging in the Naga hills to the east of Kohima. The Japanese mounted two resupply missions, using captured Jeeps to carry supplies forward from the Chindwin river to the 31^st Division, but they brought mainly artillery and anti-tank ammunition rather than food.

By the middle of May, Sato’s troops were starving. He considered that Mutaguchi and the headquarters of the 15^th Army were taking little notice of his situation, as they had issued several confusing and contradictory orders to him during April. Because the main attack on Imphal faltered around the middle of April, Mutaguchi wished the 31^st Division, or at least parts of it, to join the attack on Imphal from the north, even while the division was struggling to capture and hold Kohima. Sato considered that the 15^th Army headquarters were issuing unrealistic orders to his division without proper planning or consideration for the conditions. Nor did he believe that they were exerting themselves to move supplies to his division. Sato therefore began to consider pulling his troops back to allow resupply.

On 25 May, Sato notified the 15^th Army headquarters that he would withdraw on 1 June, unless his division received supplies. Finally on 31 May, he abandoned Naga Village and other positions to the north of the road despite orders from Mutaguchi to hang on to his position. (For a divisional commander to retreat without orders or authorisation from his superior was unknown in the Imperial Japanese army.) This allowed the XXXIII Corps to outflank Miyazaki’s position on the Aradura Spur and begin pushing to the south.

Miyazaki’s detachment continued to fight rearguard actions and demolish bridges along the road to Imphal, but was eventually driven off the road and forced to retreat to the east. The remainder of the Japanese division retreated painfully to the south but found very little to eat, as most of what few supplies had been brought forward across the Chindwin river had been consumed by other Japanese units, who were as desperately hungry as Sato’s men. Many of the 31^st Division's men were too weak to drag themselves farther to the south than Ukhrul, near the Sangshak battlefield, where hospitals had been set up, but with no medicines, medical staff or food, or Humine 20 miles (32 km) to the south of Ukhrul, where Sato vainly hoped to find supplies.

The XXXIII Corps followed the retreating Japanese. The British 2^nd Division advanced down the main road, while the Indian 7^th Division, using mules and Jeeps for most of its transport, moved through the rough terrain to the east of the road. On 22 June, the leading troops of British 2^nd Division met the main body of Indian 5^th Division advancing to the north from Imphal at Milestone 109, 30 miles (48 km) to the south of Kohima. The siege of Imphal was over, and truck convoys quickly carried vital heavy supplies to the troops at Imphal.

During the 'Battle of Kohima', the British and Indian forces had lost 4,064 men killed, missing or wounded. Against this the Japanese had lost 5,764 battle casualties in the Kohima area, and many of the 31^st Division's men subsequently died of disease or starvation, or took their own lives.

After ignoring the 15^th Army's orders for several weeks, Sato was removed from command of the 31^st Division on 5 July. The entire Japanese offensive was broken off at the same time. Slim derided Sato as the most unenterprising of his opponents, and had even dissuaded the RAF from bombing Sato’s headquarters because he wanted him kept alive, as doing so would help the Allied cause. However, Japanese sources blame Sato’s superior, Mutaguchi, for both the weaknesses of the original plan and the antipathy between himself and Sato which led the latter to concentrate on saving his division rather than driving on distant objectives.

After Sato had been removed from command, he refused an invitation to commit seppuku and demanded a court martial to clear his name and make public his complaints about the 15^th Army's headquarters. At Kawabe’s prompting, Sato was declared to have suffered a mental breakdown and was therefore unfit to stand trial. He was replaced as commander of the 31^st Division by Lieutenant General Tsuchitaro Kawada. Miyazaki was promoted to lieutenant general and given command of the 54^th Division, which was serving in Arakan.

The huge losses the Japanese suffered in the 'Battle of Imphal' and 'Battle of Kohima', mainly as a result of starvation and disease, crippled their defence of Burma against Allied attacks during the following year.

On the British side, Grover was dismissed from command of the British 2^nd Division on 5 July for perceived slowness in conducting the offensive, and also after complaints about his handling of Indian formations (Indian 161^st and 33^rd Brigades) attached to his division, and replaced by Major General C. G. G. Nicholson. Grover accepted his dismissal stoically and was appointed Director of Army Welfare Services at the War Office. Warren, who commanded the Indian 161^st Brigade during the siege, was promoted to command the Indian 5^th Division, but was killed in an air crash during the following year.

The aerial resupply of Kohima was part of an effort that, at its peak, delivered about 500 tons of supplies per day to Allied forces in the theatre. At the sieges of both Kohima and Imphal, the Allies relied entirely on resupply from the air by British and US aircraft flying from India until the road from the railhead at Dimapur had been cleared. At Kohima, as a result of the narrow ridgelines, accuracy in the dropping of air delivered logistics proved to be a considerable problem and as the fighting intensified and the defended area decreased, the task became still harder and more dangerous. In order to improve the accuracy of the drops, the Douglas C-47 Dakota twin-engined transports' pilots were forced to fly 'dangerously low'.

The increasing dominance of Allied air power by this stage of the Burma campaign was a major factor in helping the Allies turn the tide of the war in this theatre. Allied air supply enabled British and Indian troops to hold out in positions that they might otherwise have had to abandon for shortages of ammunition, food and water, as reinforcements and supplies could be brought in even when garrisons were surrounded and cut off. Conversely, the Japanese found their own supply situation harder to resolve and in the end it was one of the deciding factors in the battle.