The military costume of this reign was nearly that worn in the Civil Wars.
The defensive armour of the cavalry consisted of "a back, breast, and pot (helmet), the two latter to be pistol proof." As offensive arms they carried a sword and case of pistols with barrels not under 14 inches in length. The musketeers were ordered to carry a musket with a barrel not under three feet in length, a collar of bandoliers, and a sword.
During this reign the bayonet was first invented, at Bayonne, and was made like a dagger, with a round wooden hilt, screwed or merely stuck into the muzzle of the gun. It is now known as a "plug bayonet." The gun could not be fired while the bayonet was fixed without the loss of the bayonet also.
(Fig. 1): Henry, Prince of Wales, eldest son of James I. (from Drayton's "Polyolbion"), showing the amount of armour that was generally worn. The Prince wears only armour to the waist, with large, bombasted trunk hose, and is represented as balancing a pike. (Fig. 2): Costume, with armour of "Ferdinand, Lord Fairfax, the father of the more celebrated Parliamentary General, who also served in the same cause, and was appointed General for the County of York." He wears as armour only the cuirass and gauntlets. (Figs. 3 and 4): Plug bayonets (the earliest form), invented at Bayonne; formerly in the Meyrick collection. (Fig. 5): Single-barred helmet with "lobster-tail" neck piece and ear-pieces, usually worn by dragoons. (Fig. 6): Helmet with triple bars which protect the face, as worn by harquebussiers in 1645. (Fig. 7): Pot helmet or open head-piece, with cheeks, and a fluted ornament over the top, of the time of Cromwell. (Fig. 8): Close helmet of the time of Charles I., with ear-pieces and a perforated vizor which may be drawn down to cover the face. (Fig. 9): A "sweyne's feather" or "hog's bristle," a kind of rapier, carried by the musketeer for his defence. (Fig. 10): Effigy of Sir Denner Strutt, 1641, from his tomb in Whatley Church, Essex, illustrating the armour of the period as worn by officers in the field. (Fig. 11): A pikeman of the time of James I. (from a broadside in the possession of the Society of Antiquaries). He wears a morion-shaped helmet with plumes, back and breast plates reaching to the waist, with two broad tassets fastened to the breast plate over padded knee breeches. He is armed with a long pike and sword. (Fig. 12): A musketeer of the time of James I. (from the same source as Fig. 11). Musketeers at first wore morions on the head, but, later on, large hats with plumes were adopted. This one is represented as wearing only back and breast plates, and he is armed with a musket and a sword. In his right hand he carries a rest for his musket, and slung over his shoulder he wears a bandolier or set of leather cases, in each of which a complete change of powder for a musket was carried, to facilitate the loading of the piece. This was used until the end of the 17th century, when the cartridge-box came into use.]