A video depicting the defense of an American base from incoming Taliban rockets has gone viral, gaining more than 6 million views every day.

The video, which was uploaded a year ago, shows a C-RAM weapon system wreaking havoc in the night.

The radar-controlled rapid-fire 20mm gun is formidable, to say the least. It’s comprised of an M61 Vulcan, placed on top of a swiveling base, a potent radar. With a jaw-dropping capability of firing 4,500 rounds per minute, the C-RAM, which stands for Counter-Rocket, Artillery, and Mortar, can counter anything from enemy aircraft to missiles to rockets to artillery shells.

The C-RAM is mounted on a trailer and can be fired remotely. When a threat is spotted, the weapon system automatically detects, evaluates, tracks, engages, and conducts battle-damage assessment.

But it was the U.S. Navy that first developed the weapon system as an air-defense platform. The Phalanx CIWS, the Navy-variant of the weapon system, is nicknamed “R2-D2,” a reference to the lovable robot of Star Wars fame. Its purpose on Naval vessels is to shoot down anti-ship missiles as they approach. It can also be used to fend off enemy gunboats or suicide boats, like the ones the Iranian Navy is using or the one that rammed USS Cole and almost sunk it back in 2000. Every surface vessel in the U.S. Navy sports the C-RAM, as do some U.S. Coast Guard ships. The weapon system is also popular among other navies, including the Royal Navy, Hellenic Navy, Japanese Navy, and Royal Australian Navy.

In 1996, the C-RAM showed its devastating effectiveness but in an unfortunate manner. The U.S. Navy was conducting joint exercises with the Japanese Navy in the Pacific Ocean. During a gunnery training event, an American A-6 Intruder was towing a radar target that would act as the “enemy” for the C-RAM of a Japanese destroyer. The weapons officer on board the Japanese vessel, however, gave the order to shoot before the A-6 had time to exit the engagement envelope (in rough terms, the field wherein the missile/weapons system can be effective). As a result, the Phalanx shot down both the radar target and the A-6; the two-man crew managed to eject safely.

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The only major difference between C-RAM and CIWS is the type of ammunition used. The land version uses 20mm HEIT-SD (high-explosive incendiary tracer, self-destruct) cartridges, whereas the Naval version shoots Tungsten ammo. The reason behind C-RAM’s usage of the HEIT-SD round is that since the weapon system is often operated in urban areas, stray rounds could cause unintended collateral damage.

The U.S. military has only one another weapon system that can out-shoot the Phalanx in terms of rounds-per-minute. This is no other than the M134 Minigun, which can dish out 6,000 rounds per minute. However, the M134 Minigun, which can be mounted from helicopters to Humvees, shoots the 7.62 mm round, which is almost half the size of the 20mm.

Here is another video that breaks down the history and deployment of the C-RAM.