When tanks were first deployed in WWI, their sole purpose was to help support infantry. Even as the Germans pioneered new Blitzkrieg tactics in WWII that gave the tank new roles, the tanks of WWII were still used in many occasions in the infantry support role. Since the best way to support infantry was to get rid of enemy infantry, the best thing to equip a tank with to help it support infantry was the weapon all infantry dread; the machine gun.

Machine guns are considered fully automatic because they fire, reload, and repeat (at an alarming rate) without requiring any human input other than squeezing the trigger. Machine guns are very useful at supressing infantry, since anybody who wants to stick their head up is going to get torn to pieces by a wall of bullets.

Tanks often sported multiple machine guns. Almost all tanks had one on the leading edge of the front of the tank. Although the mounting was different on different variants, this machine gun was universally used to help get rid of unwanted enemy infantrymen that were in front of the tank (see top right picture)

A second machine gun was often mounted on the turret of the tank . German tanks, for example, almost universally sported a machine gun to the immediate side of the main gun (see top right picture), allowing the gunner to hammer a target with both machine gun fire and the fire from the main gun. Some Soviet tanks included a machine gun built into the turret, but these were normally located on the back of the turret (see bottom right picture). The turret was rotated 180 degrees so that its rear (and the machine gun) was facing whatever the commander wanted to get rid of. Other Soviet tanks featured a free motion (it had a wide range of motion) machine gun mounted on top of the turret, enabling a very brave tank commander (who else would expose themselves to enemy fire by popping out of the hatch) to inflict a world of hurt on targets without being restricted to the limited movement capabilities of the tank's normal machine guns.

HOW TO LOCATE A TANK'S MACHINE GUNS

The placement of machine guns varies wildly from tank to tank in the Sovet arsenal, although German tanks tend to have their machine guns in the same place; look for them on the leading edge of the front of the tank and on the front of the turret. Be warned; the machine guns on the front of the turret are notoriously small and hard to find. On Soviet tanks, make sure to also check the back of the turret or on top of the turret for machine guns.