Machine guns of the period operated either by recoil or by gas. Recoil-operated machine guns, such as the German MG-34 and MG-42, often had high rates of fire. When the cartridge was fired, the recoil was used to eject the spent cartridge by pushing the breechblock rearward against a spring, after a suitable safety delay period. The spring then forced the breechblock forward again and in so doing reloaded the weapon, which fired as soon as the breech was locked. Gas-operated weapons used gas from the cartridge discharge, which was bled off from a gas port in the barrel. This operated a gas piston, which interacted with the breechblock to extract and reload the weapon.
Machine guns were classified in the period after World War I as either heavy or light. The heavy versions were still mounted on tripods, equipped with both direct and indirect sighting methods, and used for direct shooting and long-range interdictory fire. The light machine guns, however, were the weapons used prolifically by the infantry. These weapons were often but not always fed by magazines or cartridge strips. They were fitted with bipod legs and could be carried in battle by one man. Normally, because of the high rate of ammunition expenditure, one or two other men accompanied the light machine gunner, carrying spare ammunition and sometimes spare barrels.
Ammunition was supplied to the machine gun in various ways. One method was the strip, in which a number of rounds were held on a metal base that was fed through the gun and then reloaded when empty. This method was used with the French Hotchkiss, the Italian Breda, and the Japanese heavy machine gun. Another method was the magazine, which was a spring-loaded box or drum fitted to the gun that could be replaced when empty. Magazines held about 30 rounds of ammunition, and weapons so fitted included the British Bren, the French M-1931A, the American BAR, the Soviet DP (Degtyarev Pekhotniya [Obratsa] or Degtyarev Infantry [Pattern]) (as a drum), and the Japanese type-96 and similar weapons.
Belt feeds, which allowed sustained long-range fire, were found, for example, on the Browning M-1917AI and M-1919A4 .30 caliber machine guns, the German MG-34 and MG-42, the British Besa 7.92 mm gun (mainly used as coaxial tank armament), and the Italian 8 mm Fiat Model 35 machine gun.
One other method was used—the clip box. This box, which held ammunition in rifle clips that were fed automatically into the gun, was a rarity. It was seen on the Japanese Nambu 6.5 mm and the Italian Revelli 6.5 mm. Feed and supply problems rendered these weapons inefficient, and they were soon phased out.
The light machine gun was issued on the basis of one weapon to every 7 to 10 men, meaning that every infantry platoon had three or four lmgs; infantry could also call on support from the heavy machine guns if needed. World War II infantry tactics were based on fire and movement, with the lmg firing and the riflemen of a section moving or vice versa. In the British army during the war, the lmg was considered a support weapon, allowing the riflemen to close on the enemy and to attack with the bayonet. The Germans also saw the lmg as the weapon with which to win a firefight with the enemy, who was then to be rolled up by the infantrymen in the section.
U.S. Army infantry troops were equipped with the BAR of World War I fame as well as light machine guns. The M-1917 series water-cooled, .30 caliber Browning lmg was used by U.S. units throughout the war. It was belt fed and could be carried in the platoon, as well as fitted to just about every vehicle in or near the front line. It led to the M-1919 series, .30 caliber, air-cooled machine guns that were the principal U.S. machine guns of the war. They were only moderately accurate, as they had no butt stock to allow effective fire control but instead were fired with a pistol grip at the rear of the gun body. Backing up these weapons was the .50 caliber Browning. The M-1921 series was originally a water-cooled weapon developed to attack aircraft and observation balloons. Its air-cooled offspring, the M-2 series "Ma Deuce," was used by every U.S. branch in every environment and theater of the war. It could be fired from a tripod mount or fixed on vehicles and could be set for single-shot fire, although it was not intended for use against personnel. The M-2 .50 caliber was also fitted in a number of aircraft. It is still issued to many armies today.
British infantry used the Lewis gun initially, but this weapon was rapidly replaced by the Enfield version of an lmg produced on license from the Brno arms firm of Czechoslovakia. Known as the Bren gun, it was regarded by many as the finest lmg ever made. The Bren was a .303 caliber, detachable-box, magazine-fed, gas-operated weapon with a rate of fire of 450 to 540 rounds per minute. It was accurate and had a very quick barrel-change system that coped with rapid firing. The Bren gun served throughout World War II and was well respected, although its rate of fire and the tactical restrictions placed on it meant that it was no match in a firefight with its German equivalent. The British also used the famous Vickers .303 machine gun in a support role.
The Soviets began the war with heavy, wheel-mounted, and shield-protected Maxim M-1910 machine guns, but experience with the Germans led to the rapid development of the DP, a section automatic weapon, fed with 7.62 mm rounds from a top-mounted round drum with a capacity of 47 rounds. This weapon was increasingly backed up by the submachine gun, which meant that the firepower of a Soviet section began to approximate that of a German infantry section, although weight and rate of fire figures were still lower.
Machine guns were not only used by the infantry, however. They were also mounted in tanks for protection against infantry, although the Germans' self-propelled Ferdinand gun was not so fitted; as a consequence, German troops suffered greatly from Soviet infantry attacks during the Battle of Kursk. Most tanks had a coaxial rifle caliber machine gun fitted in the turret and another in the hull, the latter operated by the driver, codriver, or radio operator. These machine guns were of great value in suppressing enemy machine guns and artillery when use of the main armament was ineffective or impossible.
The Americans and Germans also linked two or more machine guns for antiaircraft use. Early in the war, the Germans had a small infantry cart fitted with two MG-34 machine guns and the appropriate sights for antiaircraft defense; it was soon found, however, that the cart was too easy a target for the aircraft themselves, and the idea was discontinued. U.S. tanks were equipped with .50 caliber machine guns for antiaircraft defense, the gun being fitted above the commander's cupola on the tank and capable of a 360-degree traverse and a 90-degree elevation. Although the .50 caliber machine gun was a formidable weapon, it had few antiaircraft successes and was often used in the ground role for attacking soft-skinned vehicles and buildings.
Aircraft were also fitted with machine guns. The British Spitfire, for example, carried eight .303 caliber machine guns, but these were short-ranged and relatively ineffective against German aircraft. The British also employed the .303 caliber machine gun for bomber defense. The Americans entered the war with the .50 caliber weapon in their aircraft, which could inflict great damage on German and Japanese fighter aircraft. The Germans, however, were using 20 mm and 30 mm cannon from the start, and they soon learned that one hit from such a weapon was worth more than any number of .303 rounds and even a good burst of .50 caliber ammunition.
The British turned to the 20 mm cannon for later versions of their fighter aircraft, and the weapon proved singularly effective. The smaller caliber also meant that more ammunition could be carried per gun as compared with the German 30 mm cannon, but the Germans turned to another air weapon—the antiaircraft rocket. American fighter aircraft, however, continued to utilize the .50 caliber gun.
Naval use of machine guns was limited, although early World War II warships carried some machine guns for local protection. It was soon found, however, that much heavier weapons were needed for antiaircraft protection, and in most cases, the light and heavy machine guns went into lockers. Naval aircraft reflected their ground-based counterparts in terms of the weapons fitted on them. David Westwood
Allen, W. G. B. Pistols, Rifles and Machine Guns. London: EUP, 1953.; Daniker, Gustav. Die Maschinenwaffen im Rahmen der Taktik. Berlin: E. S. Mittler and Sohn, 1942.; Smith, W. H. B., and Joseph Edward Smith. Small Arms of the World: A Basic Manual of Small Arms. 9th ed. Harrisburg, PA: Stackpole Books, 1969.