World War II engulfed much of Europe from the late 1930s until 1945. When Japan attacked the American base at Pearl Harbor, Hawaii, in 1941, the United States joined the fight. The war saw the development of new weapons and the refinement of older designs. Time-tested designs included handguns, rifles, grenades and cannon.

Rifled Barrels and Smooth-Bore Guns

Military small arms -- such as handguns and rifles -- had rifled barrels with grooves carved in a spiral pattern inside the bore or barrel of the barrel. This grooved pattern causes the bullet to twist and spiral as it flies to the target, providing greater accuracy. Most artillery weapons such as cannons have no rifling and are considered smooth-bore weapons. Their accuracy relies on the speed at which the projectile flies toward the target.

Handguns

World War II American military officers and non-commissioned officers like sergeants were issued handguns, some of which were revolvers and some were semi-automatic. A revolver carries its bullets in a cylinder that rotates the bullets into firing position. A semi-automatic handgun carries its bullets in a magazine inserted in the lower part of the weapon. Each bullet is moved into firing position by the action of the gases released by the preceding bullet. Caliber measures a bullet’s diameter, so a .45 caliber is .45 inches wide. WWII American handguns fired .45 caliber bullets. Many enlisted men acquired handguns as well.

Rifles

The standard weapon for the Army and Marines was the rifle, including the Springfield bolt-action rifle; the semi-automatic Model 1, or M1, Garand; and the lightweight M1 carbine – all .30 caliber weapons. The bolt-action rifle advances its bullets into firing position with a handle action that must be manipulated after each shot. It is the sniper weapon of choice, but was complex to operate under fire for the average infantryman and could shoot only one round at a time. The semi-automatic M1 Garand was simpler, and its 15-round magazine could produce a hail of bullets. The shorter, lighter weight M1 carbine was issued to support units. It was produced with 15- or 30-round versions, and was manufactured by a variety of companies, proving that it was as easy to manufacture as it was to fire.

Machine Guns

While the M1 Garand and the M1 Carbine had rapid-fire capabilities, the military’s original fully automatic weapon was the Thompson submachine gun. Nicknamed the “Tommy gun,” it was capable of delivering 500 rounds per minute from its 50- or 100-round magazines. The M3A1 automatic was a short-barreled, lightweight .45 caliber weapon affectionately known as the “grease gun” because of its resemblance to the automotive garage implement. The Browning automatic rifle, or B.A.R., used .30 caliber armor-piercing rounds. It weighed about 40 pounds, so one or two were used by a squad of eight to 24 men. The .50 caliber Browning Model 2 was suitable for mounting on tanks and aircraft.

Artillery

Artillery guns, such as mortars, howitzers and cannons, are smooth-bore weapons without barrel rifling. But what they lack in rifling they make up for in muzzle velocity, or the speed that their projectiles leave the barrel. With a history dating to medieval siege warfare, the mortar is a simple tube that was still used in WWII. But its more portable and powerful brother, the 2.36-inch shoulder-fired rocket launcher known as the Bazooka was the anti-tank choice. The even larger howitzers were short-ranged but lightweight cannons and could be easily broken down for transportation by pack animal or aircraft. The 31-ton, 120MM cannon was a truck-towed ant-aircraft gun that could hit its target at 60,000 feet.