existed, including the serpentine, ribaudequin and cropaudin. The powder was of poor quality and was used in small quantities – to prevent explosion of the barrel – so the effective range of these cannon was rarely more than 200–250m. The barrels of the cannon were forged or cast, and each gun generally differed in calibre and length. Early powder resembled a paste, and tended to burn slowly. Its composition varied in different geographical areas, the powder of Europe being quite different to that used in the Islamic world. The projectiles used were generally stone balls for bombards and mortars. Forged iron balls were used in smaller-calibre cannon, and coated with lead to make them smooth. From the 15th century, cast iron balls were used, which caused great destruction. As they were denser than stone, even small balls could be destructive. Thus, cannon became smaller in calibre, and longer barrels increased the range. Later development The use of incendiary devices had decreased by the 14th century, perhaps due to the economic realities of war where it became increasingly important that captured castles and towns were undamaged. Moreover, fewer wooden engines and structures were employed in the battlefield after the late 13th century, perhaps because of the prior success of the incendiary weapons at destroying them. While the incidence of use dropped, towards the latter end of the Middle Ages the incendiary devices became more sophisticated, and the principle of wielding fire with sword remained present throughout the Early Modern and Modern periods; improving technology merely allowed the process to become more efficient. The principle of fire and sword Fire itself remained a part of warfare. In his reminisces of the Peninsular War (1807–1814), a British soldier recorded that the French soldiers would "regularly burn to the ground every place they pass through. In following them we find each town and village a heap of smoking ruins." During World War I, Leuven, in Belgium was "looted and burned in medieval fashion", when German soldiers set fire to much of the town, destroying the library and other cultural buildings, and causing outrage around the world. Yet the tactic was not dispensed with. In World War II, firebombing with incendiary bombs was carried out by the Germans against Britain during the Blitz, and by the Allies against Germany and Japan. After one heavy raid on Tokyo in March 1945, the resulting conflagration destroyed a