Mobile artillery came on the field with the cart guns of John Zizka during the Hussite Wars of Bohemia (1419-24). Using light guns, hauled by the best of horses instead of the usual oxen, the French further improved field artillery, and maneuverable French guns proved to be an excellent means for breaking up heavy masses of pikemen in the Italian campaigns of the early 1500's. The Germans under Maximilian I, however, took the armament leadership away from the French with guns that ranged 1,500 yards and with men who had earned the reputation of being the best gunners in Europe. Then about 1525 the famous Spanish Square of heavily armed pikemen and musketeers began to dominate the battlefield. In the face of musketry, field artillery declined. Although artillery had achieved some mobility, carriages were still cumbrous. To move a heavy English cannon, even over good ground, it took 23 horses; a culverin needed nine beasts. Ammunition--mainly cast-iron round shot, the bomb (an iron shell filled with gunpowder), canister (a can filled with small projectiles), and grape shot (a cluster of iron balls)--was carried the primitive way, in wheelbarrows and carts or on a man's back. The gunner's pace was the measure of field artillery's speed: the gunner _walked_ beside his gun! Furthermore, some of these experts were getting along in years. During Elizabeth's reign several of the gunners at the Tower of London were over 90 years old. Lacking mobility, guns were captured and recaptured with every changing sweep of the battle; so for the artillerist generally, this was a difficult period. The actual commander of artillery was usually a soldier; but transport and drivers were still hired, and the drivers naturally had a layman's attitude toward battle. Even the gunners, those civilian artists who owed no special duty to the prince, were concerned mainly over the safety of their pieces--and their hides, since artillerists who stuck with their guns were apt to be picked off by an enemy musketeer. Fusilier companies were organized as artillery guards, but their job was as much to keep the gun crew from running away as to protect them from the enemy. [Illustration: Figure 5--FIFTEENTH-CENTURY BREECHLOADER.] So, during 400 years, cannon had changed from the little vases, valuable chiefly for making noise, into the largest caliber weapons ever built, and then from the bombards into smaller, more powerful cannon. The gun of 1600 could throw a shot almost as far as the gun of 1850; not in fire power, but in mobility, organization, and tactics was artillery undeveloped. Because artillery lacked these things, the pike and musket were supreme on the battlefield. THE SEVENTEENTH CENTURY AND GUSTAVUS ADOLPHUS