The true story of the Assassins. Originally a persecuted band of Ismailis, a Shi’ite Muslim sect, they found themselves vastly outnumbered by the Sunnis of medieval Persia. So they developed a special way of fighting back - killing their enemies’ leaders by using stealth, infiltration and their skills with a dagger (image shows an assassin receiving a dagger for his first mission in Persia). They would go on to murder the King of the Crusaders on the eve of his coronation.

How the training of the Spartan 300 is bizarrely similar to that of today’s special forces. Here we see the distinctive Spartan helmet (pictured) protects them from spear thrusts and sword strikes. Within this battled hardened group of of warriors was an elite of the elite- the Krypteia – a secret death squad. The story goes that they set out to kill the invading Persian Emperor.

The specialist hit squads that wreaked havoc against the Roman invaders in Jerusalem. This deadly band of stealthy assassins would eventually be cornered in the mighty hilltop fortress of Masada. What happened next has horrified and fascinated the world ever since. Image shows the ruins at Masada with the Dead Sea in background.

The Germanic Ghost Warriors were one of the first special forces trained to fight specifically at night. They emerged out of the fiercely independent tribes of Germania, the wild lands to the North of the Roman Empire. When a huge Roman Army came to conquer their territory, the Ghost Warriors helped inflict the worst defeat in Roman history.

The Viking Beserkers were the elite shock-troops of Viking warlords. Fuelled by alcohol, religious fervour and possibly hallucinogenic magic mushrooms, they believed they could adopt the spirits of wild animals. One single Viking Beserker, after working himself up into a frenzy, held up an entire Saxon army with just an axe.

Vikings for hire, ruthless mercenaries who strike fear into their enemies. The elite special forces in service to a foreign ruler. Conquering unruly territories across the great byzantine empire. They are known The Varangian Guard. But its one particular man who will solidify their place in history. He will develop tactics that will form warfare across the Mediterranean. Hardrada's string of victories will show The Varangian Guard to be one of the most exceptional special forces of all time.

A special class of infantry soldier in the Aztec army and one of two military orders in Aztec society, the Eagle Warrior, or cuāuhocēlōtl, was an elite military order made up of the bravest soldiers of noble birth. The "Eagles" were soldiers of the sun, for the eagle was the symbol of the sun. The life of Aztec warriors was one of constant battle, as the primary purpose for this continual warfare was to take prisoners to be sacrificed to their gods. Of the Aztec warrior societies, the Eagle Warriors were known to take the most prisoners in battle and therefore the most feared.

The Hawaiian Koa were elite warriors in a land dominated by war. They were grand masters of a martial art called Lua- a way to break every bone in an enemy's body. When Captain Cook lands on Hawaii, the Koa warriors greet him in the worst way.

In 1562, a young warlord, called Tokugawa Ieyasu hires a specialist called Hattori Hanzo to help him free his daughters who are being held hostage in a castle. Through a hard journey, they end up inaugurating a golden era for Japan and the Ninja.

Its 1703, the Shogun is plunged into controversy when Samurai prince, Asano Naganori, loses his temper and attacks a senior official. This is the story of how Asano’s followers, the 47 Ronin, braved Japan and mounted the perfect Black Op.