At some point in our lives we will all feel strongly about an issue, enough to take arms (action).

Sir Henry Percy (1364-1403 CE) was the most famous member of the noble Percy family of northern England. Sir Henry was another knight who enjoyed success on both the tournament circuit and the battlefield. In 1377 CE, he was knighted at just age 13 by the English king Edward III and promptly helped his father recapture Berwick Castle from the Scots the next year. 1380 CE saw him on campaign in Ireland, and in 1383 CE he was crusading against pagan Lithuanians in Prussia. Two years later he was back patrolling the Scottish borders after being made the Warden of the East March by Richard II of England (r. 1377-1399 CE).

Shot by an arrow and beheaded for treason.

Sir Henry was at the Battle of Otterburn in Scotland in 1388 CE, an episode recorded for posterity in a poem by the 18th-century CE poet Robert Burns. The English lost, and Sir Henry was captured and put up for ransom, the money being raised by the king and Parliament.

Sir Henry was anything but grateful, though, and with his father he plotted against Henry IV of England (r. 1399-1413 CE), and that after helping the English king gain his throne, recapturing Conway Castle from the irksome Welsh in 1401 CE and defeating the even more troublesome Scots at the Battle of Homildon Hill in 1402 CE.

The Percy's were miffed at Henry's lack of gratitude, but the 'hotspur' - called so by the Scots for the speed with which he moved his armies and attacked - died in battle at Shrewsbury while fighting the king's forces in 1403 CE. According to legend, Sir Henry was killed by a lucky arrow which struck him in the mouth when he momentarily opened his visor. The king did not forgive his disloyalty, and Henry's corpse was quartered and his head put on a spike at the gates of York as a warning that even great knights must always serve their sovereign.

HISTORICAL LEGENDS

Saint George is based on a soldier in the Roman army who was martyred in 303 CE (Patron saint of knights)
Sir Galahad - Knight of the Round Table 12-15th century CE literature (King Arthur legend)
Siegfried - Brunhilde & King Gunter (Kriemhild, Burgundian [Nibelung] princess) c. 1200 CE


HISTORICAL KNIGHTS

Robert Guiscard - 'The Crafty' (c. 1015-1085 CE) [Norman]
Rodrigo Díaz de Vivar - 'El Cid' (1043-1099 CE)
Godfrey of Bouillon - The Swan Knight (circa 1060-1100)
Sir William Marshal - 'The Greatest Knight that Ever Lived' (c. 1146-1219 CE)
Richard I - 'The Lionhearted' (1157-1199 CE) King of England from 1189 to 1199 CE
Sir William Wallace - Braveheart (c. 1270-1305 CE)
Sir James Douglas - 'The Black Douglas' (c. 1286-1330 CE)
Bertrand du Guesclin - 'The Eagle of Brittany' (c. 1320-1380 CE)
Edward of Woodstock - 'The Black Prince' [of Wales] (1330-1376 CE) 
Sir Henry Percy - 'Hotspur' (1364-1403 CE)