Source: http://en.wikipedia.org/wiki/Mechanized_infantry
Mechanized infantry are infantry equipped with armored
personnel carriers (APCs) or infantry fighting
vehicles (IFVs) for transport and combat (see also mechanized
force).
Mechanized infantry is distinguished from motorized infantry in that
its vehicles provide a degree of protection from hostile fire, as
opposed to "soft-skinned" wheeled vehicles (trucks or jeeps) for
motorized infantry. Most APCs and IFVs are fully tracked, or are
all-wheel drive vehicles (6×6 or 8×8), for mobility across rough
ground. Some nations distinguish between mechanized and
armoured infantry, designating troops carried by
APCs as mechanized and those in IFVs as armoured.
The support weapons for mechanized infantry are also provided
with motorized transport, or are built directly into combat
vehicles, in order to keep pace with the mechanized infantry in
combat. For units equipped with most types of APC or any type of
IFV, fire support weapons, such as machine guns, autocannons, small-bore direct-fire howitzers, and even anti-tank guided
missiles, are often mounted directly on the infantry's own
transport vehicles.
Compared with "light" truck-mobile infantry, mechanized infantry
can maintain rapid tactical movement and (if mounted in IFVs)
possess more integral firepower. They require more combat supplies
(ammunition and especially fuel) and ordnance supplies (spare
vehicle components), and a comparatively larger proportion of their
manpower is required to crew and maintain the vehicles. For
example, most APCs mount a section of seven or eight infantrymen,
but have a crew of two. Most IFVs only carry six or seven infantry,
but require a crew of three. To be effective in the field,
mechanized units also require large numbers of mechanics with
specialized maintenance and recovery vehicles and equipment. Light
infantry are more effective when fighting from prepared defence
positions, but are more vulnerable than mechanized infantry on the
attack.
