The Merkava is the innovative Israeli design of Major General Israel Tal. The primary design criteria was crew survivability. Every part of the overall design is expected to contribute to helping the crew survive. The engine is in the front to provide protection to the crew.
There is a special protective umbrella for the tank commander to enable protection from indirect fire with the hatches open. Special "spaced armor" is in use along with protected fuel and ammo compartments.
Rear ammunition stowage is combined with a rear entrance and exit.
Since the rounds are stowed in containers that can be removed from the vehicle whenever necessary, this space can accommodate tank crewmen who have been forced to abandon their vehicles, or, if thought to be appropriate, even infantrymen.
Rear ammunition stowage allows replenishment much more easily than if rounds have to be replaced in a carousel in the hull center, as in typical Russian vehicles.
Tank soldiers have long admired Merkava's rear entrance and exit, recognizing that it would allow them to mount and dismount unobserved by the enemy and would provide an excellent alternative escape route.
The Merkava can also carry a small Infantry squad internally under complete armored protection.