With the arrival of the tank on World War 1 (1914-1918) battlefields, there proved a need to develop portable armor counters beyond traditional land mines and artillery pieces. Anti-tank rifles were the beginning and these were soon joined by rifle-launched grenades also intended for the anti-tank role. World War 2 (1939-1945) saw widespread use of rifle grenades and several anti-tank models were featured in the conflict (including anti-personnel forms). During the post-war years, with war against the Soviet Union (with their large fleet of heavily-armored tanks) a very real possibility across Europe, the "ENERGA" Anti-Tank Rifle Grenade emerged from Belgium. Its design was attributed to Edgar Brandt, the same French engineer responsible for the famous line of Brandt infantry mortars which were widely adopted and copied the world over. Production was handled by Mecar SA and service entry was during the early 1950s. The weapon was adopted by several foreign military powers including the United States and Great Britain.
The ENERGA rifle grenade was given a missile-style form with a conical warhead, rounded, tapering body, cylindrical tail section and finned tail arrangement. The fins added the needed stability during the grenade's flight path. The warhead filling consisted of 314 grams of Pentaerythritol Teranitrate - otherwise abbreviated as "PETN" - which gave the grenade considerable explosive power. Penetration of armor was rated up to nearly 8 inches thick - though environmental factors and angle of attack were key considerations. Overall weight reached 765 grams and the grenade featured a length of 425mm with a diameter of 75mm. Effective range was approximately 100 meters.
Such anti-tank weapons were not strictly limited to armor-defeating use for their penetration values and damage capabilities proved capable of engaging fortified structures as well - suitable for tackling dug-in foes under concrete protection. Beyond the standard ENERGA grenade form there was the "Super ENERGA" which added a small rocket booster element, increasing engagement ranges and penetration values.
In the U.S. Army inventory, the Belgian ENERGA became the "M28" and these were in action during the Korean War (1950-1953) when it was discovered that World War 2-era anti-tank rifle grenades then in service proved lacking against stouter Soviet-originated tank armor used by the North Koreans and China. Similarly, the weapon was adopted by the British Army under the designation of "Projector No. 4, Rifle, Mk V". South Africa produced a localized, slightly modified ENERGA form as the "R1M1" under the Denel brand label. These featured the same penetration value as the Super ENERGA but held a much lower effective range of just 75 meters (as opposed to 200 meters). For the Americans, the M28 was succeeded by the M31 HEAT rifle grenade. Anti-tank rifle grenades like the ENERGA were largely superseded by more potent, man-portable, shoulder-fired weapons like the disposable M72 LAW or reusable 84mm "Carl Gustav" which could engage both armor and fortifications with greater power. These weapons did, however, require line-of-sight fire.
The ENERGA name stemmed from the Liechtenstein design concern of "Anstalt fur die ENtwicklung von ERfindungen und Gewerblichen Anwendungen".