Cannon had been the backbone of the world’s artillery units for 500 years before World War II. They continued in that role throughout the war itself. When handled by skilled crews, cannon remained unmatched in their ability to deliver accurate, sustained, heavy fire from a distance. Cannon also, however, retained their traditional shortcomings. They were complex and expensive to manufacture, difficult to move on short notice, and (because of their ferocious recoil) capable of being fired only from a solid foundation.
Rocket launchers were less technologically sophisticated than even the simplest cannon. Most consisted of little more than a set of launching rails or tubes, mounted in parallel on a metal frame that could be rotated or tilted in order to aim them. Most of the rockets they fired were equally straightforward: unguided, solid-propellant weapons with diameters under 6 inches and warheads measured in tens of pounds. The individual barrage rockets fired in World War II used more potent propellants and explosives, and more sophisticated fuses, than the barrage rockets of the nineteenth century. Barrage rockets as a system, were still nearly as simple as the system developed by Congreve in the early 1800s.
Barrage rockets’ simplicity made them an ideal battlefield complement to large cannon. Because they were not precision machines, rocket launchers could be built quickly and cheaply in virtually any well-equipped factory. Because they were relatively light and produced no recoil, they could be mounted on any vehicle larger than a motorcycle. The ease of building and deploying rocket launchers encouraged commanders on both sides of World War II to bombard enemy positions with rockets as a prelude to attack. Electric ignition systems, standard by the 1940s, facilitated such barrages by allowing the rockets from a single launcher to be “ripple fired”-launched one after another at precise split-second intervals. Ripple firing multiplied the psychological impact of rocket barrages, subjecting the target to a steady cascade of explosions.
Germany began developing rocket artillery in the 1930s, as part of the rearmament program begun by the Nazis. The standard German army rocket launcher, first deployed in 1940, consisted of six short, wide tubes arranged in a circular cluster (like chambers in the cylinder of a revolver) and mounted on a lightweight gun carriage. The launcher looked like a stubby six-barreled cannon, and with good reason: it was adapted from a mortar designed to lob smoke and gas shells onto enemy positions. Its name-Nebelwerfer (smoke thrower)-was a legacy of that early stage in its development, and was retained as a way of masking the weapon’s true function. The Nebelwerfer was far from an ideal weapon: its range was limited, its accuracy was atrocious, and the 300-yard smoke trails of its rockets instantly revealed its position for enemy gunners. Like the military rockets of earlier centuries, however, its projectiles took a psychological toll as well as a physical one. Rifle and machine gun bullets, moving at supersonic speed, were invisible, but the Nebelwerfer’s rockets arced toward their targets whistling and trailing smoke. Soldiers under attack by them could only take cover and wait for impact, knowing that if they survived they’d have to do it all again moments later. Even those who were not physically injured suffered intense emotional stress.
The Nebelwerfer’s capacity for physical destruction was also impressive. The original six-tube model could launch six 150 mm rockets, each with a 5.5-pound warhead, in under ten seconds. The later five-tube model, which fired 210 mm rockets with 22-pound warheads, could hit even harder (although even less accurately). A battery of well-concealed, well-positioned Nebelwerfers could saturate a large area with high explosive in a matter of seconds. Used against soldiers massed for an attack, they could be deadly, as Allied troops discovered after the invasion of Normandy in 1944.
The Soviet Union’s prewar involvement in rocket research and its preference for simple, robust, mass-produced weapons made it, too, a natural setting for the development of barrage rockets. The Soviet army was the first to deploy a vehicle-mounted multiple-rocket launcher, a weapon that Soviet troops called the Katyusha (roughly, “Little Katie”) and their German adversaries called the “Stalin Organ.” The Katyusha consisted of eight parallel steel rails roughly 18 feet long, mounted atop a steel frame that lifted them above the vehicle and held them at the desired launch angle (usually about 30 degrees above horizontal). Each rail carried two rockets: one attached to its top edge and one to its bottom edge. Each rocket, a little over 6 feet long and 5 inches (132 mm) in diameter, could carry a 44-pound warhead about 5 miles. The rockets were inaccurate but, especially when fired in massive quantities at the beginning of an attack, highly effective at breaking up German defenses. Designed in 1938-1939 and tested in December 1939, they were first used in combat during the German invasion of the Soviet Union in the summer of 1941 and remained in active service throughout the war. Katyushas could be mounted on tanks or other tracked vehicles, but they were most often mounted on ordinary military trucks- a cheap, durable, readily available platform.
The U. S. Army experimented along similar lines, producing a variety of vehicle-mounted launchers. The first to enter service was the T27 Xylophone, named for the side-by-side arrangement of its eight launching tubes. Variations on the theme included the T27-E2 (a twenty-four-tube successor to Xylophone), the T44 (a 120-tube launcher fitted to amphibious trucks like the DUKW), and the T45 (a fourteen-tube launcher for mounting on jeeps). The most innovative launcher in the U. S. Army inventory was the T34 Calliope: a sixty-tube launcher mounted, in a wooden frame, on the turret of a Sherman tank. Calliope had two significant advantages over truck-mounted systems. First, because the launcher turned with the turret and raised or lowered with the tank’s main gun, it could be aimed quickly and easily. Second, compared to trucks and jeeps, tanks were better equipped to withstand enemy counterattacks and fight on their own once their rockets had been fired. Calliope-equipped Shermans were, in theory, capable of jettisoning their launchers in a matter of moments and becoming ordinary tanks again. Until the last months of the war, all U. S. Army rocket launchers fired the standard M8 4.5-inch rocket: short-ranged and highly inaccurate, but effective as a barrage weapon.
The Army’s attitude toward multiple-rocket launchers was ambivalent at best. On one hand, the launchers were deployed in both the European and Pacific theaters, and at least one complete artillery battalion was equipped with them. They were used in combat from June 1944 onward, but nearly all multiple-rocket launchers carried official designations beginning with T (for “test”)-a sign that they were regarded only as a temporary experiment.
The U. S. Navy and Marine Corps, by contrast, embraced rocket artillery and made extensive use of it. The Marines saw lightweight, vehicle-mounted rocket launchers as artillery support that could be brought into action quickly when assaulting enemy-held beaches. Their training school for rocketeers, established on the Hawaiian island of Oahu early in 1944, graduated its first class in April of that year. The first of six “provisional rocket detachments” was formed the same week. Each detachment consisted of one officer, fifty-seven enlisted men, and (initially) a dozen 1-ton trucks with 1-ton trailers. All six rocket detachments eventually saw action in the Pacific, first at the invasion of Saipan in June 1944 and later in the invasion of the Philippines in late 1944 and the invasions of Iwo Jima and Okinawa in 1945. The Marines developed their rocket tactics through trial and error, learning from battlefield experience how to use rocket artillery most effectively. The most critical lessons involved the vulnerability of the launchers and the unarmored trucks that carried them. The Marines originally deployed their launchers ahead of the front line of troops to maximize range, but soon shifted them back to protect the rocketeers from being overrun by the enemy. They also learned, as Army rocketeers in Europe had learned, to move their launchers immediately after firing in order to avoid “counter-battery fire” by enemy artillery and mortars. Photographs show that the Marines experimented with tank-mounted launchers (offering both protection and mobility), but there is no official record of such a program.
The U. S. Navy’s commitment to barrage rockets was even stronger. Indeed, the United States led the world in developing rockets as a naval bombardment weapon. Rockets’ relatively light weight and minimal recoil enabled the Navy to mount them on landing craft originally designed to ferry troops onto enemy-held beaches. Rocket-firing landing craft filled a crucial role in amphibious invasions. Designed to operate in shallow water, they could accompany the invasion force to the beach and blanket it with high explosives just moments before the first troops went ashore. Conventional naval bombardment-cannon fire from battleships, cruisers, and destroyers stationed offshore-had to be halted or moved inland when the invasion force neared the beach, for fear of hitting friendly troops. Rocket barrages fired from incoming landing craft could hit the beach itself moments before the assault troops. Enemy troops would thus be forced to remain under cover longer, making it more difficult for them to mount an organized, effective defense.
The Navy first used rocket barrages during Operation Torch-the invasion of North Africa-in 1942, and they soon become a standard part of amphibious operations. They were used extensively in the invasions of Normandy and southern France in 1944, and in virtually every Pacific theater invasion from January 1944 on. The vessels used ranged from Landing Craft Infantry (Rocket) carrying launchers for sixty 5-inch rockets up to Landing Ships Medium (Rocket) carrying launchers for nearly 500. The landings at Iwo Jima in February 1945 were preceded by two complete barrages fired by a line of twelve LSM(R)s. The destructive power of such a bombardment was staggering: more than 10,000 rockets poured onto the beach in a matter of minutes. The psychological effect was equally so: thousands of screaming projectiles trailing fire and smoke as they arced across the sky.