Dictated by functionality rather than fashion, armor fell into gradual decline during the seventeenth century, first in quality, later also in quantity. The weight of field armor was greatly increased in order to render it bulletproof against ever more accurate firearms. At the same time, however, the full suit of armor became increasingly rare, not only because of the amplified weight but also because of changes in tactics. Most fighting men, including their leaders, began to abandon what they viewed as excessive equipment, with only vital parts of the body, such as the head, torso, and hands, remaining protected by metal armor. A few masters, mostly court armorers, continued to produce armor of superior quality for more illustrious clients of the European nobility, but such examples were the exception rather than the rule. The growing demand to fit out large standing armies with armor at low cost (and, consequently, low quality) drastically curbed the influence fashion had on armor, although even so-called munition armor was still modeled after contemporary male costume. In shape, the breastplate began to appear squarer, while the former “peascod” profile became flatter, retaining a distinct medial ridge that now ended in a short, sharp point in line with the lower edge of the breastplate. The tassets (defenses for the upper thighs attached to the breastplate) became large in size and mirrored the exuberant emphasis on the broad hips found in contemporary fashion.
Only three elements of armor survived the gradual decline of field armor well into the nineteenth century, and to some extent even today. Helmets and breastplates continued to be worn by soldiers, but rather than being custom-made and subjected to the changing influences of fashion, their appearance came to be dictated by other factors. While changes in the shape of the helmet were determined by functionality and national identity, the breastplate was largely preserved in the shape of the seventeenth century, and—after the mid-nineteenth century—was retained almost exclusively for representative purposes. A similar fate was shared by the gorget, or collar (the neck defense). Its front plate continued to be worn only by high-ranking officers, less for the protection of the upper chest and throat than to denote rank as well as a claim of succession to a chivalrous tradition that had long since passed.
Breiding, Dirk H. “Fashion in European Armor, 1600–1700.” In Heilbrunn Timeline of Art History. New York: The Metropolitan Museum of Art, 2000–. http://www.metmuseum.org/toah/hd/afas17/hd_afas17.htm (October 2004)