In the 7th century, petroleum was among the essential ingredients for Greek fire, an incendiary projectile weapon that was used by Byzantine Greeks against Arab ships, which were then attacking Constantinople.[16] Crude oil was also distilled by Persian chemists, with clear descriptions given in Arabic handbooks such as those of Abu Bakr al-Razi (Rhazes).[17] The streets of Baghdad were paved with tar, derived from petroleum that became accessible from natural fields in the region.