Warmatrix

The main battle tank, also called 'universal tank', is the dominant type of tank today. It combines the firepower of earlier heavy tanks with the mobility of light ones.
During World War II the firepower of both tanks and anti-tank weapons increased rendered light tanks obsolete. However heavy tanks too fell out of favor because they were too slow to fight long-ranging battles and proved just as vulnerable to anti-tank fire as lighter types. The result was that only one type of tanks remained, which sits between the medium and heavy categories of the world war. These came to be called 'main battle tanks' and remain the dominant category until this day. A typical modern main battle tank weighs 45 - 70 tons and can reach speeds of about 65 kilometers per hour on roads. It fulfills all tank roles of the various types of tanks used in the two world wars.
The first tanks labeled as main battle tanks, like American M60 Patton and the Soviet T-64, appeared in the early 1960's CE. They never saw action on a grand scale like in World War II, but participated in numerous smaller conflicts. The USSR made main battle tanks the center of its armed forces.
Throughout the Cold War the threat of anti-tank weapons grew. An increase in use of of shaped charges, often called High Explosive Anti-Tank (HEAT) missiles, forced tank designers to improve the armor of their vehicles, dramatically increasing their effectiveness. They first came up with spaced armor, where a first layer of steel catches the energy of a HEAT missile and the second protects the inside of the tank. Next was composite armor, a sandwich of steel and ceramics that is even more effective against incoming fire. The 1980's CE saw the introduction of (explosive) reactive armor that partially explodes outwards when hit, largely offsetting the impact of an incoming round. The threat of attack helicopters prompted sturdy armor on all sides of the tanks, not just the front. The latest development is active protection systems, a mishmash of stealth features, radar, several types of decoys and anti-missile guns, all designed to avert a hit on the tank rather than absorb it.
On the offensive side, main battle tanks are equipped with heavier guns than their World War II predecessors, now typically ranging between 90 and 130 millimeters in caliber. They carry 30 - 50 rounds of ammunition of several types, including high explosive, HEAT and bunker-busters. The guns have range finders, thermal imagers, stabilizers and computerized fire control, allowing them to fire accurately while driving, turning and bumping around, both in daylight and at night. Some have automated loading systems, eliminating the need for a human loader, allowing the gun turret to be decreased in size. A few types do not use a conventional gun, but fire guided missiles. All main battle tanks carry 1 - 4 machine guns for close combat and often an anti-aircraft gun as a last defense against helicopters and aircraft.
Despite all improvements, the basic design of tank, ripened during World War II, remains unchanged. Though anti-tank weapons have reduced the tank from a leading role on the battlefield to just one of many combined arms, it remains a formidable weapon to this day. Most armies are unwilling to abolish it, though in the 21st century CE there is a tendency towards lighter, cheaper designs.