Mobility in military terms refers to the ability of a weapon system, combat unit or armed force to move toward a military objective. Combat forces with a higher mobility are able to move more quickly, and/or across more hostile terrain, than forces with lower mobility.
Mobility is regarded as a vital component of the modern battlefield, as the ability to deliver weapon systems or combat units to their objective quickly can often mean the difference between victory and defeat. Armies around the world have massively increased their mobility over the last one hundred years. In World War I, for example, most combat units could only move on the battlefield as fast as a soldier could walk, resulting in stalemate and an inability to outmaneuver the enemy. By World War II, battlefield mobility had greatly improved with the development of the tank, and with tracked and other mechanized vehicles to move forces to and from the battlefront.
Since the end of World War II, armies have continued to develop their mobility. By the 1980s, for example, intercontinental travel shifted from sea to air transport, enabling military forces to move from one part of the world to another within hours or days instead of weeks. Mobility has also been referred to as a combat multiplier. A highly mobile unit can use its mobility to engage multiples of its own combat strength of less mobile units i.e.; German panzer divisions in World War II were considered the equivalent of two or three infantry divisions partly due to their superior mobility and partly due to inherently greater firepower.
Mobility has also been defined in terms of three generally recognized levels of warfare: tactical, operational, and strategic. Tactical mobility is usually defined as the ability to move under fire. Operational mobility is usually defined as the ability to move men and materiel to the decisive point of battle. Strategic mobility is the ability to move an army to the area of operations.
In World War I, most armies lacked tactical mobility but enjoyed good strategic mobility through the use of railroads thus leading to a situation where armies could be deployed to the front with ease and rapidity, but once they reached the front became bogged down by their inability to move under fire.