In the Italian wars between France and Spain, in the beginning of the sixteenth century, the difficulty of moving the heavy cannon then in use was so great that only a very small number of pieces were brought upon the battle-field.  At the battle of Cerignola, in 1503, the number of cannon in the French army was only thirteen.  Indeed, during the greater part of this century, four or five pieces were considered sufficient for an ordinary army in the field, and many agreed to the doctrine of Machiavelli, that the only legitimate use of artillery was in the attack and defence of places.  But in the wars of Henry IV. of France, this arm of service was again increased, and the troops which this king destined against the house of Austria had an artillery train of fifty pieces.  Great improvements were also made about this period in the manufacture of powder, and all kinds of fire-arms.  Sully gave greater development to this arm of service, improving its materials, and increasing its efficiency.  Then, as at most other periods, the French were in advance of most other nations in artillery.

It was near the close of the sixteenth or the beginning of the seventeenth century, that the heavy and ill-shaped artillery began to give place to more wieldy and useful pieces.  A certain M. de Linar demonstrated, in the latter part of the sixteenth century, that cannon twelve feet in length would give a greater range than those seventeen feet in length, the calibre being the same; but some years elapsed before advantage was taken of this discovery.  In 1624, Gustavus Adolphus caused experiments to be made to verify this point, and, on being convinced of its truth, caused his batteries to be furnished with shorter and lighter pieces.  This great king introduced, about the same time, a new and lighter kind of artillery, made of sheet iron and leather.  Each piece had its chamber formed of thin metal and embraced by strong iron rings; over these was placed a form of hardened leather, which was again encircled with rings and held compactly together.  These pieces were mounted on light carriages, so that two men could easily manoeuvre them.  It was said that they would fire from eight to ten rounds without requiring repairs.  Gustavus made use of them in all his military operations from 1628 to the time of his death.  They did him excellent service on numerous occasions; being so very light they could be easily transported, and, on the field of battle, their movements could be made to conform to the movements of his troops.

As cannon and small arms were gradually introduced into general use, various inventions and improvements were proposed and introduced from time to time.  Cannon were constructed with two or more barrels; some were arranged for being loaded in the breech, and others at the mouth of the piece; two pieces were sometimes connected by horizontal timbers, which revolved about a vertical axis, so that the recoil of one piece would