Infantry is the most basic unit in the entire game cheap to make and always available. The player will have the option to make this unit as soon as he begins to play.
Infantry is the backbone of most anrmed forces and is usually common for starting players.
Infantry is weak by itself but good as a support unit for other land units such as Light and Heavy Tanks.
Do not expect Infantry to win by itself against other light units (ex. Motorized Infantry) because infantry is too weak unless its fighting trucks or other infantry units.
Costs very little Oil to move.