“Slim’s Boxes” and the Second Battle of Arakan

by Quin Cho

In December 1941, the Imperial Japanese Army embarked on the so-called "Nanshin-ron" or "Strike South" Campaign. The Strike South Campaign included attacks against Euro-American colonies in Southeast Asia, including the Philippines, the Dutch East Indies, British Malaya, Singapore, and Burma (contemporary Myanmar). The Imperial Japanese Army needed to capture these colonies because of their abundance of raw materials, including rubber, tin, and oil. These resources were vital to Japan's war effort in China.​

The Imperial Japanese Army's doctrine of "sokusen sokketsu" or rapid warfare, emphasized rapid maneuvers of light infantry around one or both enemy flanks to envelop or cut off the enemy, even when greatly outnumbered (Drea, 112). After the enemy was enveloped, he could be finished off and annihilated at close quarters, at which point superior Japanese elan and morale would win out (Drea, 112). Japanese infantry training also emphasized the value of night attacks, surprise, and shock in overwhelming enemy defenses (Drea, 113). Therefore, Japanese infantry doctrine at the tactical level emphasized the seizure of offensive initiative and the fast movement of light infantry to unhinge enemy defenses.
In the Strike South campaign, the Japanese put their infantry doctrine into practice to great effect, particularly in Malaya and Burma. In both British colonies, fast-moving Japanese light infantry formations‒often using bicycles for transport‒consistently outflanked and or enveloped static British defensive positions through jungles or bodies of water (Pike, 237). These formations would set up roadblocks behind British positions and used captured British supplies to sustain their advance (Pike, 272-273). Upon realizing the Japanese outflanked them, the British units would embark on panicked withdrawals (Beevor, 262). It is noteworthy that British garrisons in both Malaya and Burma directly played into the hands of the Imperial Japanese Army, as many of their formations were "road-bound," which is a disadvantage as they are overly dependent on motor transport. This feature led them to be focused on defending roads and cleared areas at the expense of adjacent rough terrain features, e.g., jungles (Frank, 383).
Furthermore, many British formations were dangerously overextended and forced to defend long or dispersed frontages on the frontiers and beaches of Malaya and Burma (Pike, 237). Such long and scattered frontages meant that British defenses had many gaps, little depth, and minimal reserves to check rapid Japanese outflanking maneuvers in many places. Therefore, the British units in Malaya and Burma were routed and/or annihilated in their engagements with Japanese units during December 1941 and early 1942.
The humiliating defeats in Malaya and Burma were a nasty shock to the British Empire. The British Army needed immediate solutions to stem the Imperial Japanese Army's light infantry tactics predicated on rapid maneuver, aggressive flanking maneuvers, and movement through rough terrain features. William Slim—the newfound commander of the Commonwealth 14th Army in India—sought to find just a solution. Slim spoke to a Chinese officer who mentioned that the main weakness of Japan's light infantry columns was their "very small administrative margin of safety," which is a reference to the supply limitations of these columns (Slim, 18). These "supply limitations" were the result of the Japanese infantry doctrine, which emphasized rapid movement and maneuver ("traveling light" allowed Japanese infantry units to move swiftly). Traveling light meant that the Japanese were often dependent on capturing enemy supplies to sustain operations beyond nine days (Slim, 18). The Chinese officer noted that it was necessary to contain the Japanese advance for a prolonged period and then counterattack them once they ran out of supplies (Slim, 18). Only then could their outflanking maneuvers be checked and defeated.
Slim used the information he learned from the unnamed Chinese officer to formulate the "Box" as a tactical countermeasure to Japanese outflanking maneuvers. The "Box" was a series of all-around perimeter defenses at the tactical level (Pike, 710). Instead of forming a long, drawn-out frontline vulnerable to exploitation of gaps and flanking maneuvers, Slim's "Boxes" would concede the Japanese temporary freedom of maneuver but also would defend vital rear area installations (e.g., headquarters, essential lines of communication, and supply depots) from Japanese attacks (Pike, 710). Panicked withdrawals would not occur as they had in 1941 and 1942. British units would hold their ground, considering the Japanese units in their rear--as opposed to themselves--to be cut off (Slim, 142-143). The British could hold their ground because they could be resupplied by transport aircraft (Britain had air superiority in Burma by 1944) (Pike, 710). 
Meanwhile, the Japanese would be forced to assault British "boxes" to attain supplies from British stores and to establish a line of communication with their compatriots attacking the British from the front (Tactics and Strategy of the Japanese Army of the Burma Campaign, November 1943 to September 1944, 12-14). Such attacks would peter out against prepared British perimeters, which would force them into static positional warfare that de-emphasized Japanese centers of gravity (initiative, light infantry maneuver, and elan), but also played on the Japanese weaknesses, namely lack of firepower and logistical support (Tactics and Strategy of the Japanese Army of the Burma Campaign, November 1943 to September 1944, 12). Moreover, if the Japanese failed to capture British supplies within the first 7-9 days of an operation (what Slim referred to as their "administrative margin of safety"), the Japanese units that flanked British positions and got behind them would themselves be cut off from resupply (Slim, 18). Under such conditions, the Japanese units that flanked British positions would starve and use British reserves to annihilate them.
The Second Battle of Arakan began with a British offensive in southern Burma called the "Arakan" with the 5th and 7th Indian Divisions in November 1943 (Tactics and Strategy of the Japanese Army in the Burma Campaign from November 1943 to September 1944, 12). The British commander of the 5th Infantry Division, Harold Briggs, attempted several fruitless frontal assaults against prepared Japanese positions (Pike, 713). Predictably, these attacks fizzled in Japanese interlocking bunkers and sophisticated trench systems (Pike, 713). The failure of the British offensive meant that they would be forced onto the defensive in the Arakan and that the Japanese would have the offensive initiative. Consequently, the Japanese began planning one of their classic outflanking maneuvers that had worked so well in Malaya and Burma in 1941 and 1942; a portion of the Japanese force would "fix" the 5th and 7th Indian Divisions in place while a 7,000 strong force would outflank these divisions and threaten their lines of communication (Pike, 713). 

British troops in Burma, 1944

The Japanese began their planned offensive on February 4, 1944. At first, all went well, as the Japanese cut off the 7th Infantry Division's line of communication through the Ngadayuek pass and threatened the 5th Indian Division's line of Bazaar-Mangdaw road that served as the 5th Indian Division's line of communication (Tactics and Strategy of the Japanese Army in the Burma Campaign November 1943 to September 1944, 12). Nevertheless, these formations did not engage in panicked withdrawals the way their contemporaries in 1941 and 1942 did (Pike, 714). Instead, they held their ground and formed all-around defensive perimeters: "Slim Boxes" (Pike, 714). These "Boxes" were sustained by aerial resupply to the tune of 1,600 tons per day for twenty-one days (Pike, 714). "Slim's Boxes" also was able to hold out against repeated Japanese assaults from both front and rear. In addition, Slim's insistence on training rear area personnel for combat was vital in helping the British hold onto important rear area installations, e.g., supply depots and headquarters. At the same time, the Japanese' lack of firepower limited their ability to suppress prepared British positions (Tactics and Strategy of the Japanese Army of the Burma Campaign, November 1943 to September 1944). Such realities meant the Japanese could not capture the vital British supply depot at Sinzweya (Pike, 714).
The inability of the Japanese to capture Sinzweya doomed their forces in the British rear area (namely the 7,000 Japanese that outflanked British positions on February 4) to starvation (Pike, 714). Furthermore, in the form of the 123rd Brigade, the British reserve attacked the Japanese units caught behind British lines in concert with the 5th and 7th Indian Divisions (Pike, 715). These attacks, combined with the effects of starvation and disease, combined to claim the lives of 5,000 of the 7,000 men who originally flanked British positions on February 4, 1944 (Pike, 715). While the number of casualties inflicted was relatively small when compared with other campaigns, the Second Battle of Arakan was important because it clearly illustrated the effectiveness of "Slim's Boxes" against Japanese light infantry tactics. These "boxes" would play a vital role in the later battles of Imphal and Kohima that stemmed from the Imperial Japanese Army's foray into Eastern India.










Bibliography
Beevor, Antony. The Second World War. Weidenfeld & Nicolson, 2014.
Frank, Richard B. Tower of Skulls: a History of the Asia-Pacific War, July 1937-May 1942. W.W. Norton and Company, 2021. 
Peattie, Mark R., et al. The Battle for China: Essays on the Military History of the Sino-Japanese War of 1937-1945. Stanford University Press, 2013. 
Pike, Francis. Hirohito's War: the Pacific War, 1941-1945. Bloomsbury, 2016.
Slim, William Joseph Slim. Defeat into Victory: Battling Japan in Burma and India, 1942-1945; with a 
New Introduction by David W. Hogan Jr. Cooper Square Press, 2000
United States, Congress, United States Military Observer Group in India, and Winston Ehrmann. Tactics 
and Strategy of the Japanese Army in the Burma Campaign from November 1943 to September 
1944, vol. 1, United States Army, 1944, pp. 1–115.

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