The tank with thousand tons weight rests on a continuous chain to distribute the force exerted by the weight of the tank over a large area. As pressure is Force per unit Area. If the chain is removed the load of the tank will act on the ground through its wheels and sink on the ground where the surface is moist and loose. This will hinder the motion of the tank and in turn reduce the fighting or operational capability.Therefore , the wheels of a battle tank rests on a continuous chain where the entire weight of tank can be distributed over the entire area covered by the chain. this results in reduction of pressure due to distribution over a large area. The same system/ principle is used for various heavy equipment used in infrasture developement/constuction industries.