The Merkava has been around since 1979, when the Merkava 1 entered service. The Merkava 2 followed in 1983 and the Merkava 3 in 1990. Improvements between different versions covered most aspects of the tank. The Merkava 3 has a 1200 horsepower engine, the Merkava 4 has 1500 horsepower. The Merkava 2 had a 900 horsepower engine and a 105mm gun, while the Merkava 3 got the current 120mm gun. Armor and fire control improved with each version, although weight stayed stable (the Merkava 1 weighed 63 tons.)
Israel is producing 50-70 Merkava 4's a year and wants a total force of 400. The Merkava 4 costs about $4.5 million each. Cutting production now would save about $1.3 billion. There is also an effort to stop development of the Merkava 5. None of Israel's potential foes have anything that matches the Merkava 3, much less the Merkava 4. Egypt has American M-1 tanks, but older models. Some Persian Gulf countries have M-1s as well. But none of these Arab countries have changed their habit of poorly training their tank crews.
The success of American troops in Iraq, and the demise of the Iraqi army, is threatening continued Israeli production, which only began in 2001, of their new Merkava 4 tank. This tank is supposed to enter service in 2004. The Merkava 4 is a 65 ton vehicle, with the engine mounted in front of the turret and a compartment in the rear of the tank that can hold eight troops, or three casualties on stretchers. The tank carries 48 rounds for its 120mm gun, with ten of them in an quick loading carousel.