The Ultimate Weapon of War: Floating Tanks?
Amphibious assaults are the domain of the U.S. Marines, not the Army. But there was a period in history when the Army tried to out-do the Marines in hitting the beach—including planning how to deploy entire divisions of amphibious tanks.
Today, the whole concept seems more than a little bizarre. The Army isn’t much involved in amphibious warfare. But in the years after World War II, the ground combat branch had plenty of experience with seaborne assaults in the Pacific. Had Japan not surrendered, the United States planned to storm the home islands with hundreds of thousands of troops including more than a dozen Army divisions.
That influenced the fighting in the next war—Korea—as Army troops stormed ashore at Inchon. To many high-ranking officers it looked like “hitting the beach” would be a key Army job for decades to come.
“When World War II ended, the Army leadership believed their service should assume the amphibious warfare mission,” retired Army Col. Donald Boose, Jr. wrote in Over the Beach: U.S. Army Amphibious Operations in the Korean War. “But it was the Marine Corps that emerged from the defense unification and roles and missions struggles of the late 1940s with their amphibious warfare mission validated by Congress, the Secretary of Defense and the Joint Chiefs of Staff.”
But just in case, the Pentagon ordered the Army to be prepared—and to keep training—for amphibious warfare. This meant figuring out how to get the Army’s fearsome tanks off Navy transport ships and onto the sandy battlefields.
Then in 1952, the Army’s Armor School at Fort Knox, Kentucky published an entire study on how to use an armored division in an amphibious operation. “Armor has a place in an amphibious operation,” the officers wrote. “[But] the use of an armored division. . . is governed largely by the type and availability of the necessary equipment to get the armored vehicles. . . over the last three to six thousand yards of water from naval transports to the beach.”
One idea they proposed was divisions of floating tanks that could drive right up to the beach, fight alongside the infantry and quickly knock out any forts or other big targets.
It wasn’t a bad idea. . . in theory. The Marines today field armored, swimming troop-carrying vehicles for this purpose. Amphibious tanks had also been around for two decades by the time of the Armor School’s study. During World War II, every major combatant—except Italy—had produced some sort of floating armored vehicle.
The Soviet Union produced the first kind to go into mass production, the T-37, in 1932. Based on an experimental British design, the vehicle weighed just over three tons and had a single 7.62-millimeter machine gun. The Kremlin’s weaponeers eventually built improved designs using a different chassis. At six tons, the T-40 was the largest of these vehicles. But the Soviets pulled most of these types from front-line service early in the war.
In the Pacific, Japan had gone to war with a fleet of small and largely outdated tanks. Still, these types proved to be more than enough to help defeat Chinese and European colonial troops—at least in the beginning. In 1941, the Imperial Japanese Navy got its first Type 2 Ka-Mi amphibious tanks to help in capturing various island chains. Tokyo’s engineers created the vehicle by adding pontoons to the front and rear of a conventional Type 95 Ha-Go light tank.
Once on dry land, the crew could drop these floats and continue along their way. Twice as heavy as the T-40, the Ka-Mi had a 37-millimeter main gun and two 7.92-millimeter machine guns.
The Nazis planned to ride in submersible tanks during an invasion of the United Kingdom. Unlike other types, these vehicles would drive along the English Channel’s seabed at depths of nearly fifty feet deep using a snorkel to keep water out of the engine. They would then crawl out of the water and up the beaches toward their objectives.
It was not to be. When Hitler scuttled the proposed invasion and after brief service on the Eastern Front, the German army saw little need to keep working on these tauchpanzers.
The British and Americans came to the party relatively late. Unlike the floating Soviet tanks and the Japanese pontoons, British weaponeers chose a simpler means of getting tanks to ride on the water.
In 1940, Hungarian-born engineer Nicholas Straussler cooked up a special flotation screen known as a Duplex Drive—or DD—to keep the water out. Before driving into the water, crews would deploy this canvas screen, effectively creating a buoyant hull. Propellers pushed the vehicle along. . . and when the vehicle hit land, the screen would drop back down, out of the way.
For four years, engineers tinkered with the concept on various older tanks. In the end, British, American and Canadian troops converted their famous M-4 Sherman tanks into “DDs” for the D-Day landings in Normandy and operations elsewhere in Europe. In March 1945, the floating tanks crossed the Rhine River as Allied forces pushed deeper into Germany.
The Fort Knox study considered the DD design as a possible option for the Army’s future Cold War force. The proven gear was easy to install, had little impact on the tank’s basic performance and didn’t add significantly to the vehicle’s overall size.
Existing landing craft and amphibious ships could basically carry as many DD tanks as regular tanks. And crews could raise and lower the screen at will to cross rivers, canals or other waterways farther inland after the initial landing.