The Merkava tank was designed in the 1970s following the failure to purchase Chieftain tanks from the United Kingdom.

The Merkava was designed in the 1970s following the failure to purchase Chieftain tanks from the United Kingdom. Originally designed to duke it out with Soviet tanks in the deserts surrounding Israel, the tank was laid out in a rather unorthodox manner compared to contemporary Western and Soviet tanks, featuring a design more akin to some infantry fighting vehicles. Instead of having the engine at the rear, the engine was moved in front of the crew compartment, with the turret placed further back on the chassis.

The result was that the front armor could be more gradually sloped, and the crew could enter and exit the tank quickly from the rear.

Merkava – Tank History and Review:

However, this comes with the drawback of having the engine more easily disabled, as any penetrating front hit will disable it. Israeli doctrine prioritizes the survivability of the crew in an engagement, so in the event of a disabling hit the crew will bail out rapidly through the rear hatch if the situation allows. On the other hand, a penetrating frontal hit on a western tank will likely leave the tank still mobile.