Developed from the Viking sword and tracing its roots back to the Roman spatha, the arming sword, also known as the knightly sword, was a double-edged straight sword with a blade usually measuring between 28 to 32 inches, although some had blades of up to 39 inches, and that featured a single-handed cruciform hilt that gave it a distinctive cross shape. It was prevalent as the main European sword from the 11th to 14th centuries, after which it was edged out by the longsword and relegated to the role of a secondary weapon or sidearm – hence the name “arming sword”.
The transition from the Roman spatha-based Viking sword to the Medieval arming sword went through the intermediate phase of the Norman sword of the 9th and 10th centuries, which witnessed a simplification of the pommel to a disk or hazelnut, and the growth of the Viking sword’s spatha handguard into a full crossguard – the main visually distinguishing feature of both the arming sword and its successor, the longsword.
By the 11th century, the transformation had been completed, and the arming or knightly sword, now featuring a more slender and tapered blade than that of the Viking sword, with a sharper tip than the more rounded one of the Viking sword, and a center of mass closer to the hilt that improved the weapon’s handling, had become the dominant state of the art European sword.
Typically used with a shield or buckler, the arming sword was an excellently balanced light and versatile weapon, useful for both thrusting and cutting. It was the main weapon of the Crusader knights, and remained the most popular sword on European battlefields throughout the late Middle Ages and into the opening stages of the Hundred Years’ War. Its heyday finally came to a close in the 14th century, which witnessed changing tactics and battlefield conditions, particularly the growing use of plate armor, against which the arming sword was of little use.
Starting in the late 12th century, arming sword designs began to polarize in reaction to the increasingly tougher armor encountered on the battlefield, becoming either longer and heavier for concussive impact and the infliction of blunt trauma through the armor, or more squat and sharply pointed to pierce the armor with a thrust. By the mid 14th century, an entirely different sword, the longsword, had emerged in response to the new armor, and proved more effective at dealing with it than the arming sword could. Thus the longsword supplanted the arming sword, and the latter was relegated to a secondary weapon or sidearm.