Cultivator No. 6: The Cautionary Tale of the Brit’s Trench Digging Machine

Cultivator No. 6 was a behemoth, ahead of its time machine that emerged amidst the escalating Second World War. A brainchild of Winston Churchill, the trench digging machine was designed to break the stalemate of trench warfare that traumatized the Brits during the First World War. Not wanting a repeat of millions of casualties, Churchill sorted through previous ideas about advancing trench digging using mechanical means.

But while the First Lord of the Admiralty has a notable reputation as an outstanding problem solver and visionary, he wouldn’t predict the dramatic shift of the course of WWII. And despite recognizing that the project would be ineffective, Churchill persisted in pressing on and squandering valuable resources when Britain desperately needed them.

Churchill’s Brainchild

The year was 1939, and Germany had just invaded Poland. Prime Minister Arthur Neville Chamberlain appointed Churchill as First Lord of the Admiralty to the Cabinet. With his previous experience, the latter wasted no time devising a plan to give them an advantage in trench digging. His original concept was to have an armored trench digging machine that could burrow under the ground and dig straight through No Man’s Land, where troops and vehicles would then access the enemy line. But this wasn’t an easy feat as technology was still far from where it is today.

Nevertheless, Churchill launched the project using his prerogative and assigned the development to renowned ship engineer J.H. Hopkins under the top-secret Department of Naval Land Equipment (NLE). After numerous different designs were submitted, the engineers finally received Churchill’s approval. It was a machine resembling the rhomboid shape of the earliest Great War tanks and was slated to mass produce 240 units.

Codename the Cultivator No. 6, engineers figured that for this to actually work, they would need a power of at least 1,000 horsepower, which would be shared between moving and digging. Initially, they thought of tapping for Rolls-Royces for their latest (at that time) Merlin engine. But the Royal Air Force reserved first and was given absolute priority.

Enter Sir Harry Ricardo, a notable engineer who was among the first to develop the internal combustion engine. He suggested using two 600hp Paxman diesel engines instead, which was good because it ended up a better match. With this, the digging and automotive systems can be powered separately rather than sharing one powerplant.

Nellie, The Trench Digger

Keeping the project under wraps, the trench digging machine had several names to disguise its true purpose, including NLE Tractor, Cultivator No. 6, White Rabbit No. 6, and Nellie. Churchill also referred to it at times as his mole.

Probably paying homage to Mark I (aka Little Willie), the trench digging prototype was unofficially called Nellie (or it could be wordplay for the NLE department). Nellie had two main parts: the head, responsible for the actual digging, and the body, which provided the machine’s overall movement.

The head alone weighed around 30 tons and measured 9.3 meters (30 feet 6 inches) long, 2.6 meters (8 feet 7 inches) high, and 2.2 meters (7 feet 3 inches) wide. It also featured a large plow blade that could scoop through the upper 2 ft 6 in the soil while a rotating cutting cylinder removed the lower 2 ft dirt.

Meanwhile, the body was over 14 meters long and weighed 100 tons, resembling the Mark I. Its 2 ft wide tracks wrapped around the entire vehicle, with a top seed of 3.04 mph on the surface. A hinge connected the head to the body, allowing it to pivot up and down freely.

Nellie was a sight to behold, with an overall measurement of 23.62 m (77 ft 6 in) long and weighing 130 tons. One onlooker even saw how wide Churchill’s smile was when he saw the demonstration of the prototype, saying: “…his smile of pleasure almost dislodge his cigar.”

The massive trench digging machine had proven to do an excellent job.

Nellie could burrow about 0.5 miles of track in an hour at full speed, moving 8,000 tons of soil in the process. It would cut a trench 1.5 m (5 ft) deep and 2.3 m (7 ft 6 in) wide as it went through, while conveyors on top of the machine deposited the dirt along the sides of the trench—adding a few feet to the trench’s depth.

The prototype followed Churchill’s original concept: Nellie would start digging from friendly lines and traverse through No Man’s Island and up into the enemy lines, where troops and vehicles that followed behind could pop up and assault hostile troops. Nellie would be taking the night shift for this to happen without being bombarded.

But Nellie Never Made It To Sevice

Nellie didn’t see the light of day thanks to another inventor Cecil Vandepeer Clarke who suggested a somewhat less complicated solution: explosives.

Well, that’s just one of the factors why it didn’t see action anyway, as Clarke’s idea was eventually ditched because it would require an explosive-proof machine that could survive the explosion. Besides, in terms of stealth, Nellie has the edge. Not to mention that the Brits had already spent too much on creating the Cultivator, in addition to the fact that they were nearing a year into the war already. So starting a new project would be too late by the time it is finished.

What made them scrap Nellie altogether was in May 1940, when the Nazi Germans overran France using fast mobile warfare that ditched the trench warfare behind and subsequently placed the massive trench digging machine in obsolescence.

“The change which has come over the war affects decisively the usefulness of ‘Cultivator No. 6’. It may play its part in various operations, defensive and offensive, but it can no longer be considered the only method of breaking a fortified line. I suggest that the Minister of Supply should to-day be instructed to reduce the scheme by one half. Probably in a few days it will be to one-quarter. The spare available capacity could be turned over to tanks.”

—Churchill wrote to his chief military assistant, Major General Hastings Ismay, shortly after becoming Prime Minister

Churchill, however, had a hard time letting go of the project. He recognized that his “mole” would no longer be effective on the battlefield, yet he pushed through with the project until its completion in 1941 and was formally named NLE Trenching Machine Mark I. It stretched for another year until it was finally terminated in 1943, with only five built, including the prototype. Four of the units were eventually scrapped soon after the war, while the fifth one survived until 1950 before it met its final disposition. The nation needed the funds it could get, and Nellie definitely doesn’t need its share.

(H/T: Tank Historia)