From the requirements of the battlefield, the Merkava was designed in a rather unusual way compared to contemporary Western and Soviet tanks.
Instead of the traditional rear engine layout, the Merkava engine was positioned in front of the crew compartment, with the turret placed deeper into the chassis. The downside of this design is that it will reveal more of the infrared signature in the front hemisphere, and poor balance compared to the traditional design. The layout of the front engine also makes the tank more susceptible to disabling, any collision from the front and penetrating the engine will leave the Merkava just a useless lump of iron.
But this engine layout also has certain advantages. With the engine in front, this layout is intended to grant additional protection against a frontal attack, so as to absorb some of the force of incoming shells, especially for the personnel in the main hull, such as the driver. It also creates more space in the rear of the tank that allows increased storage capacity and a rear entrance to the main crew compartment allowing easy access under enemy fire. This allows the tank to be used as a platform for medical disembarkation, a forward command and control station, and an infantry fighting vehicle. The rear entrance’s clamshell-style doors provide overhead protection when off- and on-loading cargo and personnel.
Israel’s war doctrine is to prioritize the protection of the crew in all situations, so in the event of a hit, the crew will quickly escape through the rear door, if the situation permits. While the answer to whether the crew can get out of the vehicle in time after being hit is still controversial, it is clear that having a suitable exit will increase the survivability of the crew, especially on the empty desert battlefield.
With the rear door design, when needed, the Merkava tank can be turned into a fortress for soldiers escorting. However in the case of a total war the design is not really valuable, even the advantages of the front engine are not enough to make up for its shortcomings.
Another major issue is the ability to carry ammunition on a Merkava tank. The shells were contained in heat-resistant, flame-resistant plastic containers and stored in the compartment with the crew. This design saw the early Merkavas destroyed, not by enemy fire, but by shells in the vehicle being detonated.