It did exist! And it was called Goliath.

Goliath is a clever caterpillar robot guided with cable used by Wehrmacht during WWII. With a weight between 365 to 430 kgs depending on the model, it could remotely deploy an explosive charge of between 60 to 100kg. Its targets was usually an enemy's tank or fortress.

• It's known to have been present on landing beaches of Normandy. Fortunately for allies forces, they didn't receive proper maintenance and became fragile. As a way of proof, only one of these caterpillar-carts exploded on Utah beach. The rest were too rusty or artillery damaged their cables, making them useless.

• They were used too on the German offensive to clear of mines out an immense defensive minefield after Kursk battle.

• Later on, after Warsaw's uprising in 1994, they were used to by SS units. Polish forces, with a limited anti-tank weapons, used to send volunteers to cut Goliaths' cables before they reach their objective.