The tank, which was developed after its predecessor, the armored truck, was meant to be able to cover rough terrain due to the trench warfare. Trench warfare involves the digging of trenches to make it hard for the enemy to advance, but with the development of crude versions of the tank the trench defense system became obsolete during the end of the First World War and beginning of the Second World War. Fundamentally the tank was developed and employed to breach the enemy’s defense lines, especially during a stalemate. The tank changed warfare because it had the capacity to withstand bombardment, machine gun fire, and barbed fences. This reduced injuries and fatalities to the soldiers. Tanks were predominantly used to lead and prepare the way for the infantry units and provide cover for assault operations. The tanks developed also helped in carrying surface to air missiles to repel air attacks from the enemy, thus revolutionizing both land and air warfare.
The invention of tanks made defenisve trench networks in the style of WWI obsolete. It returned mobility to the battlefield and helped to bring about the "blitzkrieg" style of warfare that worked so well for the Germans in the early part of WWII.
Things like barbed wire and machines guns and trenches had turned warfare (from about the time of the US Civil War through WWI) into a process in which the defense had a huge advantage. Tanks changed that. They were able to drive over all sorts of terrain, including trenches and they were able to smash barbed wire. They were able to move quickly, acting as cavalry used to act.
By doing these things, tanks changed battle. This is one reason why WWII saw no repeat of the trench warfare of WWI.
At first tanks were not available so, the early kings and people used cannons and cannon balls.
But today it is modern technology. Tanks such as M1H2 Abrahms have come, and heavy vehicles like artleries have changed the world.
Today we are highly developed.
The tank emerged as the perfect fighting machine. It has armored shielding which means it can move into enemy territory without much risk to the driver and gunner. Tanks can move rapidly and hence can cover large distances, which is especially important for running through enemy lines and providing fire from the rear end of the enemy line, something that cavalry excelled at doing. It can cross trenches easily, break barbed wires and roll over other structures, making defensive warfare useless. A tank carries machine guns and cannons and thus can out-compete guns and stand-alone canons (where mobility has always been the issue).
All this made the tank a great fighting machine and changed the face of warfare. It was introduced in World War I and since then has been the mainstay of land-based warfare.