Did you know about Churchill’s “underground tank”?

British Prime Minister Winston Churchill was well-known for having very clear visions on how to overcome military problems with technology, and for his willingness to push outlandish ideas like iceberg aircraft carriers into practice, or at least testing. One of the lesser-known results of his enthusiasm for technological solutions was the Cultivator No. 6, a bizarre device sometimes described as an “underground tank” – that never saw use.
 
Early in World War II, before the German invasion of France, many believed that the war will be a replay of World War I with long static frontlines that would take a dreadful toll on manpower to break through. (Inside the World War I trenches) Churchill, still appointed First Lord of the Admiralty and not yet Prime Minister, already had experience with trench warfare in World War I, when he formed the Landships Committee, whose work led to the invention of the tank. Now he remembered an idea he had at the time.

He envisioned a tracked vehicle that could dig a trench while advancing toward the enemy lines, followed by infantry. The trench would be deep enough to keep the vehicle below ground level. Once the enemy trenches were reached, the vehicle’s top could be used by the infantry as a ramp to charge into enemy positions. The digging work would occur at night under the cover of artillery bombardment to drown out its noise and ensure surprise.
 
A secret department called the Department of Naval Land Equipment was set up to design and build the digger. The name’s abbreviation “NLE” ended up as “Nellie,” the nickname of the first prototype. The digging vehicle was referred to by various names: White Rabbit Number Six, Cultivator No. 6, N.L.E. Tractors and, when mentioned by Churchill, “mole.”

The final design was a 130-ton monster 77 ft 6 in (23.62 m) in length, 7 ft 3 in (2.21 m) wide and 10 ft 5 in (3.18 m) tall, powered by two 600 horsepower engines, one used for propulsion, the other for the digging equipment. When digging at a speed of 0.42 or 0.67 mph (0.68 or 1.08 km/h), it used a giant plow on top to remove the top two feet of the earth in front of it, and a spinning blade a bit like a lawnmower’s to remove the bottom two feet. The trench was 5 feet deep, but the excavated dirt was pushed and thrown up and to the sides, creating an additional two feet of cover at the top. The vehicle had a three-man crew. The basic version was called the “infantry” machine, and a wider, “officer” machine was also designed that could dig a trench wide enough for tanks to advance through.

200 infantry and 40 officer Cultivators were ordered initially, but the German invasion of France and the demonstration of “Blitzkrieg” proved that World War II was going to be too mobile for massive trench system, rendering the Cultivator unnecessary. Only five were ever built, and were all dismantled after the war. In his memoirs, Churchill commented on the idea: “I am responsible but impenitent.”
 
If you want to explore the tanks of World War II and other armed conflicts, join us on our Britain at War Tour to discover iconic armored vehicles at the Tank Museum in Bovington.