While light cavalry had been used in warfare for many centuries, the medieval era saw the rise of heavy cavalry, particularly the European knight. Historians are uncertain when the use of heavy cavalry in the form of mounted shock troops first occurred, but the technique had become widespread by the mid-12th century. The heavy cavalry charge itself was not a common occurrence in warfare. Pitched battles were avoided if at all possible, with most offensive warfare in the early Middle Ages taking the form of sieges, or swift mounted raids called "chevauchées", with the warriors lightly armed on swift horses and their heavy war horses safely in the stable. Pitched battles were sometimes unavoidable, but were rarely fought on land suitable for heavy cavalry. While mounted riders remained effective for initial attacks, by the 14th century, it was common for knights to dismount to fight. Horses were sent to the rear, and kept ready for pursuit.