Frederick Barbarossa - the German emperor

When Adolf Hitler named the WWII invasion of Russia, Operation Barbarossa, many people had to go back to the history books to understand. It was the largest and most violent and bloodiest campaign in the history of the war and it was named after the medieval emperor- Frederick Barbarossa.

Source
Frederick was born in 1122. In 1147 he became Duke of the southern German region of Swabia. Frederick was such a uncompromising warrior and natural leader that when King Conrad died in 1152 he snubbed his own son out of his inheritance and appointed Barbarossa king instead. The name Barbarossa is just the Italian way of saying "Red Beard" Frederick eventually got tired of the Pope’s power and decided to make the Pope understand that no matter how much moral authority he may have, He is generally the guy who makes the rules. In 1158, Barbarossa marched his armies over the Alps into Italy and started a trail of destruction on just about everything he could find. The Italian armies were crushed, and those cities foolish enough to resist the German onslaught were surrounded and besieged. Frederick, in one of his battles, tried to avoid a lengthy Siege and captured a bunch of still-breathing prisoners of war, stuffed them into catapults, and launched live civilians head-first into the enemy battlements until the defenders surrendered. He undertook six expeditions into Italy.