No tank design has ever been fielded in significant numbers that proved to be too complex or expensive to manufacture, and made unsustainable demands on the logistics services support of the armed forces. The affordability of the design therefore takes precedence over the field performance characteristics.
Firepower is the ability of a tank to identify, engage, and destroy. Protection is the tank’s ability to resist being detected, engaged, and disabled or destroyed. Mobility includes tactical (short range) movement over the battlefield including over rough terrain and obstacles, as well as strategic (long range) mobility, the ability of the tank to be transported by road, rail, sea, or air to the battlefield.
Tank design is a compromise; it is not possible to maximise firepower, protection and mobility simultaneously. For example, increasing protection by adding armour will result in an increase in weight and therefore decrease mobility; increasing firepower by installing a larger gun will force the designer to sacrifice speed or armour to compensate for the added weight and cost. Even in the case of the Abrams MBT which has good firepower, speed and armour, these advantages are counterbalanced by its notably thirsty engine, which ultimately reduces its range and in a larger sense its mobility.