The English longbow was a tall and strong bow, usually slightly taller than the archer’s height, approximately 1.70 m (5′ 6″), and shot 31-inch-long arrows, fitted with a steel arrowhead, capable of piercing a knight’s armor. It was usually made of two wood staves, with the outer one being ash sapwood and the inner one yew heartwood. At the end of a long process, the longbow was smeared with resin to make it water-resistant. These natural materials could withstand stretching and compression. The arrows were also made of ash wood and the bow string was twisted flax fiber, which was flexible and soft, yet hard. The elastic and resilient property of yew wood gave the English longbow strength and propelling power, with a range of 220 m (240 yd). When massively used, as in the Middle Ages, the thick rain of steel-tipped arrows could stop the charging mounted knights. This medieval weapon was used by the English infantry (archers) during the Hundred Years War, being decisive in some battles, especially during the battles of Crécy (1346) and Agincourt (1415).