Mortier de 15 de Vallière

Jean-Florent de Vallière was a French Royal Army veteran who served in 60 sieges and 10 battles. In 1726 he was appointed Director General of Artillery.^[2] The French guns of that era included artillery pieces that were manufactured in different countries and employed a range of various calibers. Keeping track of the different ammunition sizes was a logistical headache. On 7 October 1732, the Vallière system replaced all earlier artillery systems used by the French Royal Army. Its purpose was to reduce the number of calibers, standardize the production of the new gun barrels, and manufacture all its artillery pieces in France. The system successfully met these goals.^[3] The Vallière cannons were well designed and accurate.^[4] The Vallière system artillery included 24-pounder, 16-pounder, 12-pounder, 8-pounder and 4-pounder cannons, mortars of 12-pouce and 8-pouce, and stone-throwing (pierrier) mortars of 15-pouce.^[5]

A mortar was an artillery piece that threw an explosive projectile or stone on a high arc into enemy fortifications. A mortar was usually of short length and large caliber. It lacked wheels and was used during sieges.^[6] The Vallière guns performed well in siege warfare but proved disappointing as field artillery.^[5] Vallière believed it was foolish to make different cannons for siege and field artillery.^[7] In the War of the Austrian Succession (1740–1748) it was discovered that the new guns were appropriate for sieges, but the great weight of the 4-, 8-, and 12-pounder guns made them unsuitable for use as field artillery.^[8] To address this problem, the French manufactured some lighter 4-pounder cannons copied from a Swedish design.^[9]

During the Seven Years' War (1756–1763) the French artillery was at a serious disadvantage when facing lighter Prussian and British cannons. As a remedy, the so-called Swedish 4-pounders were again produced and employed as battalion guns.^[10] Before the war, Austria implemented the Liechtenstein artillery system which greatly improved its cannons.^[11] Even Russia introduced reforms for its obsolete cannons with the Shuvalov artillery system in 1757. ^[12] Meanwhile, Vallière was succeeded by his son Joseph as Director General of Artillery. In 1761, King Louis XV's War Minister Étienne François de Choiseul, Duke of Choiseul sent Joseph de Vallière to review the Kingdom of Spain's artillery. With the younger Vallière out of the way, Choiseul authorized Jean-Baptiste Vaquette de Gribeauval to conduct a series of tests at Strasbourg in 1765.^[13] The tests showed Gribeauval's much lighter guns could shoot just as far as the old Vallière guns.^[14] On 17 August 1765, the Vallière system was replaced by the Gribeauval system.^[15]

Note that pouce is a French inch equal to 27.07 mm (1.066 in), so that 15-pouce equals 406.05 mm (15.99 in). The livre or French pound equals 0.48941 kg (1.08 lb).^[16] The 15-pouce mortar weighed 1,000 livres or 489.41 kg (1,079 lb) and required 2.5 livres or 1.223525 kg (2.7 lb) of gunpowder to launch its stone.^[17] The pierrier mortar required a crew of three. One crew member placed the gunpowder and rammed it down with three blows. Two wads were placed atop the powder and rammed down with nine blows. The projectiles were held in place by tamped earth or dung. The stone missiles were held in baskets 15-inches wide and 20-inches deep. The vent was primed with gunpowder and ignited by a linstock. When fired, the stones scattered with the object of injuring or killing enemy personnel.^[18]