A second view, based on the fact that Greek fire was inextinguishable by water (some sources suggest that water intensified the flames) suggested that its destructive power was the result of the explosive reaction between water and quicklime. Although quicklime was certainly known and used by the Byzantines and the Arabs in warfare, the theory is refuted by literary and empirical evidence. A quicklime-based substance would have to come in contact with water to ignite, while Emperor Leo's "Tactica" indicates that Greek fire was often poured directly on the decks of enemy ships, although admittedly, decks were kept wet due to lack of sealants. Likewise, Leo describes the use of grenades, which further reinforces the view that contact with water was not necessary for the substance's ignition. Furthermore, Zenghelis (1932) pointed out that, based on experiments, the actual result of the water–quicklime reaction would be negligible in the open sea.