When we think of Special Operation Forces today, we think of Delta Force, SAS, SEALs, Rangers — you name it. Men drilled to perfection and kitted with the best technology the West has to offer. Any unit that’s classified as SOF has the capability to do some sort of Special Operations — missions that the conventional forces can’t or won’t perform.

But SOF is a quite recent classification in warfare.

A century ago, amid the horrors of World War One trench warfare, a unit, with the help of a ground-breaking (literally) invention, was created to conduct missions that the conventional forces couldn’t perform.

The Royal Tank Regiment (RTR) was created in 1916, following the invention of the tank. According to our contemporary criteria, the Royal Tank Regiment was a SOF unit in the sense that it could conduct missions that the rest of the army couldn’t — i.e., bridge the gap between the British and German trenches.

Although the first tanks were used in the Battle of the Somme in 1916, it wasn’t until the Battle of Cambrai, one hundred years ago this week, that the tank really made its debut.

On the morning of November 20, 1917, 476 British Mark IV tanks shot through the morning mist and shattered the German lines.

Their aim was to breach the powerful Hindenburg Line, the last cushion of defense between the Allies and Germany, and thus help end the war.

Although they had a promising start, the Germans promptly counter-attacked and drove them back.  The battle lasted until early December; the war wouldn’t end until almost a year later on November 11, 1918.

Moreover, the Battle of Cambrai was the first time American troops fought in the Great War. Although the U.S. had joined the Allies seven months earlier, the four U.S. divisions in France weren’t yet ready to fight and were still training. The Battle of Cambrai ended that, though it only gave significant experience to the few regiments of U.S. Army engineers involved.

Today, only seven original Mark IVs exist.

Interestingly, Mark IVs were gendered. Male versions had a six-pound gun and three machine guns and were slightly bigger, whereas female versions had six machine guns.

The anniversary of the Battle of Cambrai is a special day for the Royal Tank Regiment. On this day, wherever troops from the unit might be deployed, whether it’s in North Africa fighting Rommel or in Afghanistan ratting out Taliban, special services are always held to honor their forefathers.

This article was originally published in January 2018. It has been edited for republication.