Incendiary bombs were used extensively in World War II as an effective bombing weapon, often in a conjunction with high-explosive bombs. Probably the most famous incendiary attacks are the bombing of Dresden and the bombing of Tokyo on 10 March 1945. Many different configurations of incendiary bombs and a wide range of filling materials such as isobutyl methacrylate (IM) polymer, napalm, and similar jellied-petroleum formulas were used, many of them developed by the US Chemical Warfare Service. Different methods of delivery, e.g. small bombs, bomblet clusters and large bombs, were tested and implemented. For example, a large bomb casing was filled with small sticks of incendiary (bomblets); the casing was designed to open at altitude, scattering the bomblets in order to cover a wide area. An explosive charge would then ignite the incendiary material, often starting a raging fire. The fire would burn at extreme temperatures that could destroy most buildings made of wood or other combustible materials (buildings constructed of stone tend to resist incendiary destruction unless they are first blown open by high explosives).