lever mechanism to propel projectiles. Basically a portable trebuchet which could be operated by a single man, it was advocated by emperor Nikephoros II Phokas around 965 to disrupt enemy formations in the open field. It was also mentioned in the Taktika of general Nikephoros Ouranos (ca. 1000), and listed in the Anonymus De obsidione toleranda as a form of artillery. Greek fire: The invention and military employment of Greek fire played a crucial role in the defense of the empire against the early onslaught of the Muslim Arabs. Brought to Constantinople by a refugee from Syria by the name of Kallinikos, the incendiary weapon came just in time to save the capital from the Muslim sieges of 674–678 and 717–718, which might have otherwise proven fatal to the Byzantine state. Greek fire, referred to by Byzantine chroniclers as "sea fire" or "liquid fire", was primarily a naval weapon, used in ship-to-ship battle against enemy galleys. The exact composition was a well-guarded state secret, to the point that modern scholars continue to debate its ingredients, but the main method of projection is fairly clear, indicating effectively a flame-thrower: The liquid mixture, heated in a brazier and pressurized by means of a pump, was ejected by an operator through a siphon in any direction against the enemy. Alternatively, it could be poured down from swivel cranes or hurled in pottery grenades. Greek fire held a fearsome reputation among Byzantium's numerous enemies who began to field – probably differently composed – combustibles of their own. It was, however, no wonder weapon, but dependent on favourable conditions such as a calm sea and wind coming from behind. When and how the use of Greek fire was discontinued is not exactly known. According to one theory, the Byzantines lost the secret due to over-compartmentalization long before the 1204 sack of Constantinople. Incendiary grenade: Grenades appeared not long after the reign of Leo III (717–741), when Byzantine soldiers learned that Greek fire could not only be projected by flamethrowers, but also be thrown in stone and ceramic jars. Larger containers were hurled by catapults or trebuchets at the enemy, either ignited before release or set alight by fire arrows after impact. Grenades were later adopted for use by Muslim armies: Vessels of the characteristic spheroconical shape which many authors identify as grenade shells were found over much of the Islamic world, and a possible workshop