Leo III successfully defended Constantinople from the army of Maslama B. 'Abd. al-Malik in 717-718. Their secret weapon, "Greek Fire," played a decisive role. It was a chemical mixture that ships squirted at enemy ships through pressurized tubs. Water didn't douse its flames, so even diving into the sea didn't help, which sounds beyond horrific. Leo III tricked his enemy by promising he would let them take the city by opening the gates. He then asked them to deplete their rations so they appeared non-aggressive to the public inside. Shockingly, they fell for it. Once they destroyed their rations, he refused to open the gates and the enemy army found themselves destitute as winter began. They eventually retreated out of desperation. This was the closest anyone had come to taking Constantinople, but Leo III prevailed. He also ended the "twenty years anarchy" that saw a succession of short-lived emperors and a lot of violence. Despite all that, he did start the iconoclasm controversy that kept the empire distracted for over a century. A fascinating historical figure, but decent examples of his coins remain difficult to find. This follis is the best example I've come by in my searches. Leo III (717-741), Æ Follis, Constantinople, Obv: δNO LεON MμL., Bust facing, with short beard, wearing crown and chlamys, and holding globus cruciger and akakia; Rev: δN CONSτANτIUS, Bust of Constantine V , beardless, facing, wearing crown and chlamys, and holding globus cruciger and akakia, all above an ornate horizontal bar, beneath which large M between A/A and x/x, beneath M, A; 18mm, 2.50g; DOC 31b, Sommer 21.9, Sear 1514