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.

A look at the story of the Varangian Guard, the elite bodyguards of the Byzantine Emperor.

A look at the formidable Hawaiian Koa Warriors trained in the art of Loa, Hawaii's own martial arts.

The history of Ninja's, who first were a division of Japan's greatest Shogun.

A look at the group of 47 Ronin - dishonoured Samurais who had lost their status.