MILITARY BATTLES - BATTLE OF IMPHAL– KOHIMA

General

Figure-1: Military Battles-Indo-Burma theatre

1.      The famous battle of Imphal and Kohima was fought between the Japanese and Allied Forces during World War-II from 09 March - 19 August 1944 in the center sector of Indo-Burma theatre. It has correctly been named as ‘‘Spring Board’’ from which the final offensive for the total annihilation of the Japanese forces was launched. That resulted ultimate recapture of whole Burma.

Figure-2: Military Battles-Location of Imphal

Allied Interest or Strategic Aims of the Allied Forces

2.         Allied interest or strategic aims of the allied forces are as follows:

a.         To Keep Open an Overland Supply Route to China and Keeping China in the War with the Allies.      With the invasion of Burma by the Japanese, the Burma road from Rangoon to Yunnan was cut off and China was cut off from all surface communication. But China was fully dependent on US supply of war material. When the war between Japan and China held almost 1/3 of total Japanese land forces engaged. Thus it was very important to keep China in war with Allies and therefore an overland supply route (Hump Route) from India to China and its security was very essential. For this, the northern Burma had to be captured from the Japanese.

Figure-3: Military Battles-Supply Route to China

b.         To Secure the Hump Route.       Opening an overland supply route through India to China was a long term project but important for immediate supply and replenishment. The Hump air route over the Himalayan ranges had to be opened and therefore its security was vital. Thus it was important to capture the northern Burma from the Japanese occupation.

Figure-4: Military Battles-Hump Route

c.         To Re-conquest the Lost Territory of the British Empire.   This is obvious because Burma was a British colony and its loss would have certainly encouraged other colonies to revolt for independence.

d.         To Re-conquest the Complete South East Asia Using Burma as a Launching Pad.         Re-conquest of Burma would certainly provide a tactical viable launching pad for subsequent operations to re-conquest other occupied territory like Indo-China, Borneo, Malaya, Singapore etc.

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e.         To Defend the Indian Subcontinent.     The defense of Burma was then key for the defense of Indian subcontinent, the largest British Empire. It was also to be ensured that the Japanese does not get the opportunity of securing any kind of peace with the Allies by virtue of possessing this large mainland empire.

f.          To Enjoy the Geo-strategic Importance of Burma.   Burma was an important link in the route from Britain to Australia. There was an airport at Rangoon and many leading roads and air service also. Thus defense of this leg of the air route was strategically important for Britain.

Figure-5: Military Battles-Location of Rangoon

g.         To Draw Japanese Forces from the Pacific to Facilitate Rapid US Success in the Pacific.      War in Burma and also keeping China in war against Japan would have drawn more Japanese forces and their war material towards that theatre. This would have weakened the Japanese forces in the Pacific and facilitated rapid US success.

Figure-6: Military Battles-Pacific

Slim’s Assessment of Japanese Intention in January-February 1944

3.         In early 1944, General Slim assessed the following regarding subsequent Japanese offensive:

a.         Main offensive would be launched by Japanese 15 Corps in the center front, led by Mutaguchi with 15, 31 and 33 Division and the 1 INA Division, one tank regiment and other troops.

b.         There might be another division, not yet identified, in reserve.

c.         Japanese objectives would be, to capture Imphal first and secondly, to break through to the Brahmaputra valley so as to cut off the northern front and disrupt the air supply to China.

d.         The Japanese would isolate the forward formations and then destroy them in detail. They would attempt with a reinforced division to get behind both 17 Division on the Tiddim-Imphal road and 20 Division along Tamu-Palel road. In the meantime other Japanese columns amounting to two divisions would cross the Chindwin near Homalin and Thaungdut, make for Imphal via Ukhrul.

e.         A Japanese regiment would be poised to Kohima to cut the Kohima-Dimapur road and threaten the Dimapur base.

f.          The offensive would begin about the 15 March.

Figure-7: Military Battles-Slim's Assessment

Courses Open to Slim to Defeat Japanese Plan.

4.      General Slim had following options open to him:

         a.      To cross the Chindwin river and attack the enemy first.
         b.      To hold the enemy across the Chindwin line and destroy them while crossing.
         c.      To draw the enemy around the Imphal plain and fight a decisive battle.

Figure-8: Military Battles-Courses Open to Slim

Slim’s Plan to Defeat the Expected Japanese Offensive in Imphal-Kohima.

5.      The British forces confronting 15 Army on the Imphal front were deployed as under:

         a.      17 Indian Division (Cowan), located at Tiddin to withdraw rapidly once the Japanese attack develops and form Corps reserve at Imphal, leaving behind a brigade group some 40 miles south of Imphal to block the Japanese advance.

 b.        20 Indian Division (Grecey) was to withdraw from its forward position in Kabaw Valley and hold the Shenam Pass, dominating the Imphal-Sittaung road.

 c.        23 Division (Robert) to fall back to Imphal leaving one brigade group at Ukhrul to form Corps Offensive Reserve at Imphal with part of 17 Indian Division, 50 Para Brigade and 254 Tank Brigade.

6.     Key Aspects of the Allied Plan.

        a.      General Slim intended to allow Japanese to advance to the edge of the Imphal plains, and when committed in assault on the prepared position at Imphal, would be counter attack and destroyed by the mobile striking forces, strong in artillery, armour and air craft.

b.      Both the outlying Divisions (17 and 20) had to withdraw back to Imphal intact without any assistance from other formations or Corps Reserve.

c.      Formations of Corps Reserve were dependent on the time of arrival of committed formations away from Imphal and their success in making a clean break.

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Japanese Offensive on the Imphal-Kohima Front in 1944

Figure-9: Military Battles-Japanese Offensive

                    

7.      The U-Go Plan.          The attack on Imphal and Kohima was to be carried out by 15 Japanese Army command by Lieutenant General Mutaguchi. The essence of U-Go plan was the speed with which it was to be carried out. The plan was as follow:

         a.      31 Japanese Division (Lieutenant General Sato).           The Division was to cross the Chindwin on the night 15/16 March 1944, over run Ukhrul and seize Kohima. Sato was then to send a column to help the attack on Imphal.

         b.      15 Japanese Division (Yamauchi).       The Division was to cross the Chindwin on the same night, sending an advance guard via Ukhrul to cut the Imphal-Kohima road at Kanglatongbi. The main body was to seize the high ground north of the Imphal Plain and attack Imphal from north in conjunction with an assault from the south by 33 Division.

         c.      33 Japanese Division (Lieutenant General Yanagida).      The Division was to start the operation a week earlier than the other two divisions in order to draw Allied reserve away from Imphal and Kohima. The main force was to cut the Tiddim road behind 17 Division, destroy it and attack Imphal from the south.

         d.      Yamamoto Force.         Right column of 33 Division and INA formations were to drive 20 Division from Tamu road and attack Palel and Imphal from the south east.               

8.     Japanese Offensive.

        a.      The Japanese 33 Division started the offensive on 09 March 1944 with thrust aimed at cutting off Cowan’s 17 Division. The wdr order was given to 17 Division on 13th March 1944. Before 17 Indian Division could withdraw, the Japanese had set up number of road blocks in the rear of the division near Tonzang. Two brigades of 23 Indian Division (Reserve Division of the Corps) supported by RAF fighter were sent as reinforcement. After fighting a series of battles, 17 Division managed to withdraw to Imphal on 05 April 1944.

        b.      On night 15/16 March 1944, Yamamoto force advanced from the south towards Tamu-Palel. Despite fierce fighting, 20 Indian Division conducted much more orderly withdraw to Shenam by 02 April 1944. On 01 April 1944, 32 Brigade of this division was pulled out as Corps reserve to Palel.

        c.      Meanwhile, Japanese 31 Division crossed Chindwin in three columns from Homalin and attack on Ukhrul on 19 March which was captured by 26 March 1944.

        d.      Anticipating the situation Slim brought 5 Indian Division by air from Arakan to Imphal as reinforcement during 19-29 March 1944.

        e.      15 Japanese Division crossed Chindwin on 15/16 March at Thaungdut. On 29 March 1944, they cut off the Ukhurul-Imphal road at south of Ukhrul. It then turned south west against Imphal. At the same time 31 Japanese Division established a road block on the Imphal-Kohima road. Thus except for the Bishenpur-Silchar track to the west, Imphal was cut off.

        f.       31 Japanese Division's successful penetration to the north had by now created a more dangerous situation at Kohima. Appreciating the situation Slim ordered to bring 33 corps (Lieutenant General Stopford) from India to take command of the Dimapur-Kohima area with 2 British Division, 268 Infantry Brigade and two tank regiments.

        g.      On 26 March 1944, 161 Brigade of 5 Indian Division was flown to Dimapur to plug the gap until 33 Corps could get into position.

        h.      To further strengthen the central front, Slim also ordered the move of 7 Indian Division from Arakan and distribute two brigades to join 33 Corps at Dimapur and third brigade to 4 Corps at Imphal. Slim also pulled Wingate’s 23 Brigade from India to Jorhat to cover the Ledo railway and for use to support Dimapur.

        j.       On 04 April 1944, Japanese attack on Kohima started. General Stopford sent forward 2 British Division to join 161 Brigade. On 24 April 1944, seizure of Kohima was over.

        k.      On 09 April 1944, the Bishenpur-Silchar track had been cut off by 33 Japanese Division. On 11 April 1944, the Japanese seized Nungshigum Hill, only six miles west of Imphal airfield. It was the most dangerous threat for the maintenance of 4 Corps.  Therefore, Scoons reserve ponded quickly and recapture Nungshigum Hill on 13 April.

9.     The Counter Offensive.

         a.      On night 5/6 Jun 1944, the great Aradura Spur, 2/3 miles south of Kohima was captured. The battle of Kohima was over. 33 Corps with 2 British Division and 7 Indian Division drove down south to link up with 4 Corps.

                b.      By the first of June 1944, 5 Indian Division recaptured Kanglatongbi and advanced northward to meet 33 Corps.

        c.      On 22 June 1944, 2 British Division and 5 Indian Division joined hands 29 miles north of Imphal. The battle for Imphal was over and the isolation of 4 corps thus ended.

        d.      By 01 July 1944, Ukhrul was encircled and on 08 July 1944, it was captured by 7 and 20 Indian Division and 23 LRP Brigade.

e.      23 Indian Division reinforced with 5 Brigade of 2 British Division and 268 Indian Brigade advanced along Tamu-Palel road and captured Tamu on 04 August 1944.

f.         The order for Japanese 15 Army to withdraw back to Chindwin  was given on 09 July 44 by which time Japanese 15 and 31 Divisions were completely up routed. On 19 August 1944, the last organized Japanese units left India.

Causes of Japanese Defeat

10.    Following were the causes of Japanese defeat: 

         a.      Fighting without Reserve.     Mutaguchi committed all his forces in the opening move on his offensive, keeping no reserve for exploitation of success.

         b.      Over Optimism. The Japanese plan was over optimistic; they accepted the risk in undertaking an offensive with an overall land and air force inferiority.

         c.      Lack of Intelligence.    The Japanese command failed to appreciate the new fighting spirits of the allies and misread their enormous potentialities of air transport and supply.

        d.      Over Stretched Line of Communication.   The Japanese suffered heavily because of over stretched & tenuous lines of communication.

        e.      Rigidity in Planning.    The Japanese were very rigid in their plan and did not allow local commanders to take initiative and exploit the allied weakness in defense.

        f        Lack of Air Power.        The Japanese had, virtually no air support and the allied air force played havoc on their position and movement.

        g.      Numerical Inferiority.   Japanese had numerical inferiority against Allied. They had only three divisions against two Corps on the face of Allied air superiority.

        h.      Lack of Coordination between Central and Southern Front.   The Japanese did not have coordination and synchronization on their action in Arakan and Central Burma front.

Lessons Learnt

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11.    Following are the lessons learnt of this battle:     

         a.      The Principles of War. It should be fol as much as possible, because between two forces who will make maximum use of the principles will have victory.

        b.      Air Support.  In absence of communication over land, ground force can be supported by air.

        c.      Enemy must never be Underestimated. The clean withdrawal of 17 and 20 Divisions did not go according to the plan as Slim underestimated the speed and strength of Japanese.

        d.      Sound Logistic Plan.   Without good logistic back up, line of communication of advancing forces should never be stressed too far specially across a major obstacle. The Japanese suffered heavily because of over stretched & tenuous lines of communication.

        e.      Use of Reserve.      Reserve must be kept and used at the appropriate moment and place.

        f.       Over Optimistic Plan must be Avoided. The Japanese plan was over optimistic; they accepted the risk in undertaking an offensive with an overall land and air force inferiority.

        g.      Timely Withdraw should be Made to Conserve Combat Power for Future Operation.   A commander, when he is sure about the failure of his plan, should accept defeat and withdraw his forces to conserve it for subsequent battle.

        h.      Air supremacy.  It is an important factor in modern war. Allied could withstand prolong seizer because of air superiority. 4 Corps received on aver early 500 tons of supply by air daily.

         j.       Efficient Admin Set Up.   It is a pre-requisite for decisive success in the battle.

        k.      Flexibility in Plan and Execution.  One of the requirements for meeting the unexpected difficult situation and for the exploitation of success is flexibility. The Japanese were very rigid in their plan and did not allow local commander to take initiative and exploit the allied weakness in defense.

        l.       Cutting Off or Encirclement of Troops does not Mean Defeat or Surrender.    The Allied remained be seized for long but they did not give up.

        m.     Training of Troops.    Training as per territory forms formidable base for victory.

        n.      Morale. It is one of the battle winning factors.

        p.      Cooperation.   Cooperation between services and different forces are essential for success in the modern battle.