Hayreddin Barbarossa was a Turkish pirate who helped expand the Ottoman Empire west, turned from corsair to admiral, built the Ottoman Navy, and helped change the balance of power in the Mediterranean.
Ernle Bradford, The Sultan's Admiral
E. Hamilton Currey, Sea-Wolves of the Mediterranean
Islands and Military Orders, c.1291-c.1798, Ed: Simon Phillips
Kenneth Setton, A History of the Crusades