Before it fell for good to the Ottomans in 1453, the city of Constantinople withstood something like a dozen sieges by foreign armies over its long history. The one successful siege, by the soldiers of the Fourth Crusade in 1204, was of course eventually rolled back when the Latin Empire went defunct in 1261. But other than that, all of them were unsuccessful. Two of those failed attempts to take the city were made by Arab armies under the Umayyad Caliphate. The first attempt may have been made in 674-678 (this is generally considered the Arabs’ “first siege” of Constantinople, though it wasn’t really as cohesive as that description implies), when the Byzantines may have been saved by the advent of Greek Fire (a highly effective incendiary weapon–particularly destructive at sea, since it continued to burn even in water–whose formula is still unknown) and its use in destroying an attempted Arab naval blockade of the city sometime in 677-678.