Shermans M4A3 of A Company, 6th Tank Battalion Okinawa
The Battle of Okinawa: Combined Army-Marine Tank Operations
Overview of the Operation
The Battle of Okinawa, which began in April 1945, was the largest combined Army-Marine amphibious operation of World War II, occurring shortly after the grueling Iwo Jima campaign. As the first battle fought on Japanese soil and involving a significant civilian population, Okinawa was seen as a grim precursor to the anticipated invasion of Japan’s Home Islands.
Japanese Armored Forces
By this stage in the war, the Japanese Army had decided to conserve its remaining armor for the defense of the Home Islands. As a result, the only significant Japanese tank presence on Okinawa was the understrength 27th Tank Regiment, which fielded just 13 Type 95 Ha-Go light tanks and 14 Type 97 Shinhoto Chi-Ha medium tanks.
U.S. Tank Forces and Strategy
In contrast to the limited Japanese armor, the U.S. assembled its largest armored force of the Pacific campaign for Okinawa. This included eight Army tank battalions, two Marine tank battalions, and two Marine independent tank companies, totaling over 800 tanks, as well as numerous amphibious tanks, self-propelled (SP) guns, half-tracks, and other armored fighting vehicles (AFVs).
- Marine Tank Units: The Marine tank contingent comprised the battle-hardened 1st Tank Battalion and the inexperienced 6th Tank Battalion. The 1st Battalion was equipped with M4A2 Sherman tanks, while the 6th Battalion used the newer M4A3 model.
Tactical Innovations and Coordination
During the landing phase, an innovative experiment involving the T6 pontoon device allowed a company from each Marine tank battalion to land, though this proved unnecessary as the landings were uncontested.
- Tactical Approaches: By this point in the war, the 1st Tank Battalion had developed effective tank-infantry coordination tactics. These tactics focused on using tanks to suppress enemy positions with direct fire while infantry provided close protection against Japanese infantry assaults. Against lightly defended positions, a combination of artillery, rockets, and tank fire was used before the infantry moved in to seize the ground. For heavily fortified positions, particularly those with underground bunkers and caves, the approach involved methodical advances, with tanks clearing an area of about 500 yards at a time using a mix of direct fire and flamethrower attacks.
Marine and Army Tank Battalion Differences
The Marines’ systematic approach helped minimize tank casualties from Japanese close-in infantry attacks, a stark contrast to the Army tank battalions, which suffered heavy losses in similar situations. The main threats to Marine tanks came from mines and antitank guns, particularly the Japanese 47mm antitank gun. To counter these threats, Marine tanks increasingly added spare track blocks to their hulls and turrets for added protection. Additionally, some companies began attaching wooden frames over the suspension bogies, following the practice of the 5th Tank Battalion on Iwo Jima, to protect against Japanese soldiers placing satchel charges under the tanks.
- Flamethrower Tanks: Neither Marine tank battalion was equipped with the more powerful POA-CWS-H1 main gun flamethrowers, relying instead on the less effective E4-5 auxiliary flamethrowers. The 713th Flamethrower Tank Battalion from the Army was assigned to support the Marines, with B Company of the 713th sometimes attached to the 1st Tank Battalion and occasionally assisting the 6th Tank Battalion.
The Cost of Battle
The fighting on Okinawa was intense, with heavy tank casualties. The 1st Tank Battalion, for example, saw its operational strength drop from 47 M4A2 tanks on May 1 to just 28 tanks by June 22. The battalion suffered its heaviest losses during the battle for Kunishi Ridge in mid-June, with 21 tanks lost in a single day. Over the course of the campaign, the 1st Tank Battalion’s tanks were knocked out 163 times, with many tanks being repaired and returned to service multiple times. The battalion ultimately lost 28 of its original 47 tanks and received 38 replacements (21 M4A2s and 17 M4A3s). Overall, the combined Marine and Army tank units on Okinawa suffered 153 total tank losses, of which 51 were Marine tanks.
Despite these losses, the resilience and adaptability of the U.S. tank forces played a critical role in overcoming the well-entrenched Japanese defenses on Okinawa, contributing to the eventual American victory in one of the war’s bloodiest battles.