10 Must Brutal Acts Of Revenge In History

3. Genghis Khan Slaughtered 4 Million Khwarezmids After Having His Offer Of A Peace Treaty Rebuffed

Genghis Khan was not a particularly nice bloke, and it will not come as a shock to see his name that his names features list.

The Mongol invasion of Khwarezmia (modern-day Turkey) between 1219 and 1221 saw the expansion of Khan's empire into the Islamic states - as well as the murder of up to 4million civilians.

Originally, however, Khan wanted trade with the Khwarezmid Empire - and even sent ruler Ala ad-Din Muhammad a message stating: "I am master of the lands of the rising sun while you rule those of the setting sun. Let us conclude a firm treaty of friendship and peace."

Yet when Khan sent a caravan to the Khwarezmian city of Otrar, his Mongols were massacred - and as a result he had molten silver poured into the eyes and mouth of one of the leading enemies. Khan then lead a 200,000-strong Mongol force into Khwarezmia - storming through the entire empire, killing 1million soldiers and another 3million civilians - insisting that "not even dogs or cats" be spared.

Muhammad did escape to an island in the Caspian sea, but died penniless - in the knowledge his entire empire had been savagely reduced to smithereens by an angry Genghis Khan.