ammunition HEAT warheads were developed during
World War II, from extensive research and development into
shaped charge warheads. Shaped charge warheads were promoted internationally by the Swiss inventor
Henry Mohaupt, who exhibited the weapon before World War II. Before 1939, Mohaupt demonstrated his invention to British and French ordnance authorities. Concurrent development by the German inventors’ group of Cranz,
Schardin, and Thomanek led to the first documented use of shaped charges in warfare, during the successful assault on the fortress of
Ében Émael on 10 May 1940. Claims for priority of invention are difficult to resolve due to subsequent historic interpretations, secrecy, espionage, and international commercial interest. The first British HEAT weapon to be developed and issued was a
rifle grenade using a cup launcher on the end of the rifle barrel; the
Grenade, Rifle No. 68 /AT which was first issued to the
British Armed Forces in 1940. This has some claim to have been the first HEAT warhead and launcher in use. The design of the warhead was simple and was capable of penetrating of armor. The
fuze of the grenade was armed by removing a pin in the tail which prevented the
firing pin from flying forward. Simple fins gave it stability in the air and, provided the grenade hit the target at the proper angle of 90 degrees, the charge would be effective.
Detonation occurred on impact, when a striker in the tail of the grenade overcame the resistance of a creep spring and was thrown forward into a stab
detonator. By mid-1940, Germany introduced the first HEAT round to be fired by a gun, the 7.5 cm Gr.38 Hl/A, (later editions B and C) fired by the KwK.37 L/24 of the
Panzer IV tank and the
StuG III self-propelled gun . In mid-1941, Germany started the production of HEAT rifle-grenades, first issued to
paratroopers and, by 1942, to the regular army units (
Gewehr-Panzergranate 40,
46 and
61), but, just as did the British, soon turned to integrated warhead-delivery systems: In 1943, the
Püppchen,
Panzerschreck and
Panzerfaust were introduced. '' was lethal at close range against armored vehicles The
Panzerfaust and
Panzerschreck (tank fist and tank terror, respectively) gave the German infantryman the ability to destroy any tank on the battlefield from 50 to 150 meters with relative ease of use and training (unlike the British
PIAT). The Germans made use of large quantities of HEAT ammunition in converted
7.5 cm Pak 97/38 guns from 1942, also fabricating HEAT warheads for the
Mistel weapon. These so-called
Schwere Hohlladung (heavy shaped charge) warheads were intended for use against heavily armored
battleships. Operational versions weighed nearly two tons and were perhaps the largest HEAT warheads ever deployed. A five-ton version code-named
Beethoven was also developed. Meanwhile, the British
No. 68 AT rifle grenade was proving to be too light to deal significant damage, resulting in it rarely being used in action. Due to these limits, a new infantry anti-tank weapon was needed, and this ultimately came in the form of the "projector, infantry, anti-tank" or PIAT. By 1942, the PIAT had been developed by Major
Millis Jefferis. It was a combination of a HEAT warhead with a
spigot mortar delivery system. While cumbersome, the weapon allowed British infantry to engage armor at range for the first time. The earlier magnetic hand-mines and grenades required them to approach dangerously near. During World War II the British referred to the Monroe effect as the "cavity effect on explosives". During the war, the French communicated Mohaupt's technology to the U.S. Ordnance Department, and he was invited to the US, where he worked as a consultant on the
bazooka project. The need for a large bore made HEAT rounds relatively ineffective in existing small-caliber anti-tank guns of the era. Germany worked around this with the
Stielgranate 41, introducing a round that was placed over the end on the outside of otherwise obsolete anti-tank guns to produce a medium-range low-velocity weapon. Adaptations to existing tank guns were somewhat more difficult, although all major forces had done so by the end of the war. Since velocity has little effect on the armor-piercing ability of the round, which is defined by explosive power, HEAT rounds were particularly useful in long-range combat where slower
terminal velocity was not an issue. The Germans were again the ones to produce the most capable gun-fired HEAT rounds, using a
driving band on bearings to allow it to fly unspun from their existing rifled tank guns. The HEAT round was particularly useful to them because it allowed the low-velocity large-bore guns used on their many
assault guns to also become useful anti-tank weapons. Likewise, the Germans, Italians, and Japanese had in service many obsolescent
infantry guns, short-barreled, low-velocity artillery pieces capable of direct and indirect fire and intended for infantry support, similar in tactical role to
mortars; generally an infantry battalion had a battery of four or six. High-explosive anti-tank rounds for these old infantry guns made them semi-useful anti-tank guns, particularly the German guns (the Japanese 70 mm
Type 92 battalion gun and Italian
65 mm mountain gun also had HEAT rounds available for them by 1944 but they were not very effective). High-explosive anti-tank rounds caused a revolution in anti-tank warfare when they were first introduced in the later stages of World War II. One infantryman could effectively destroy any existing tank with a handheld weapon, thereby dramatically altering the nature of mobile operations. During World War II, weapons using HEAT warheads were termed
hollow charge or
shape charge warheads. It was this article that revealed to the American public how the fabled bazooka actually worked against tanks and that the velocity of the rocket was irrelevant. After the war, HEAT rounds became almost universal as the primary anti-tank weapon. Models of varying effectiveness were produced for almost all weapons from infantry weapons like
rifle grenades and the
M203 grenade launcher, to larger dedicated anti-tank systems like the
Carl Gustav recoilless rifle. When combined with the
wire-guided missile, infantry weapons were able to operate at long-ranges also. Anti-tank missiles altered the nature of tank warfare from the 1960s to the 1990s; due to the tremendous penetration of HEAT munitions, many post-WWII
main battle tanks, such as the
Leopard 1 and
AMX-30, were deliberately designed to carry modest armour in favour of reduced weight and better mobility. Despite subsequent developments in
vehicle armour, HEAT munitions remain effective to this day. == Design ==