An attack helicopter is a military helicopter arme for attacking targets on the ground such as enemy infantry, armored vehicles and structures, using autocannon and machine-gun fire, rockets, and precision guided missiles such as the Hellfire. Many attack helicopters are also capable of carrying air to air missiles, though mostly for purposes of self-defense. Today's attack helicopter has two main roles: first, to provide direct and accurate close air support for ground troops, and the second, in the anti tank role to destroy enemy armor concentrations. Attack helicopters are also used to supplement lighter helicopters in the armed scout role.