Swedish artillery reigned supreme in the early part of the seventeenth century. Gustavus introduced marked changes by making the guns and the carriages lighter and handier, and by adapting their movements to those of the other arms and to the requirements of the battlefield. In this, as in all his military efforts, his motto was mobility and rapidity of fire. In 1624 Gustavus had all his old types of guns recast into newer models and the following year he himself contrived a gun which three men and one horse could maneuvre to good effect. It was an iron three and four pounder with a cartridge weighing less than a pound and consisting of a charge held in a thin wooden case wired to a ball. This was the first artillery cartridge, the original fixed ammunition. The gun was afterwards used in other European armies and known as the “piece Suedoise.” Not only had it the advantage of lesser weight but its cartridge was always ready to fire and it could be fired eight times to the six times of the infantry musket of that day. In the wars against the Poles, Gustavus employed with profit the so-called leather cannon, a fact which shows how lacking the times were in artillery power. These guns were invented in the early 1620s by a Colonel Wurmbrandt, and consisted of a thin copper tube reinforced by iron bands and rings, then bound with rope set in cement, the whole covered with sole leather. The tube was made to screw in and out because it grew heated by from eight to twelve charges and had to be cooled. The gun carriage was made of two planks of oak. The gun without the carriage weighed about ninety pounds and was fired with a light charge. They were used during 1628-29 and then gave way for four pounder cast-iron guns which remained in common usage in Europe until artillery was reorganized by Frederick. Gustavus’ batteries excited universal admiration. Grape and canister were generally employed in the field guns and round shot only in the siege guns. Artillery was used massed or in groups and also with regiments of foot soldiers. Gustavus was probably the first to demonstrate the real capabilities of artillery. Mortars throwing bombs were first used at the siege of Lamotte in 1634. Hand grenades, shells, fire-balls, etc., came into more general use as the German chemists made their new discoveries. Artillery practice grew to be something of a science; experts took it up and the troops were better instructed. Regimental artillery, that is, artillery with the infantry, was attended by grenadiers detailed for the work. There were special companies for serving the reserve guns. The period following the Thirty Years’ War—the middle of the seventeenth century—gave no great improvement to the art of war but there were many marked advances in the matter of details of construction. During the era of Gustavus it was Sweden that led in making war more modern; during the era of Louis XIV it was France.