Cuirassiers were mounted cavalry soldiers equipped with armor and firearms, first appearing in late 15th-century Europe. They were the successors of the medieval armored knights. The term is derived from cuirass, the breastplate armor which they wore. Cuirassiers were generally the senior branch of the mounted arm retaining their status as heavy cavalry - "Big men on big horses". While their value as a heavy striking force in Napoleon's campaigns ensured the continued use of a number of cuirassier regiments in the French and Prussian armies during the nineteenth century.