William Marshal (1146-1219) was the son of John Marshal, a minor Anglo-Norman lord who switched sides during a period of civil wars between King Stephen of England, and Stephen's niece, Matilda (mother of the future Henry II of England). Young William was being held by Stephen as a hostage. When John Marshal turned against Stephen, Stephen laid siege to his castle (Newbury), and brought William to the site. He informed John that if he did not surrender, his son would be hanged, to which John famously replied, "Go ahead. I still have the hammer and the anvils with which to make more and better sons." Fortunately for William, Stephen did not carry out his threat.
John was only a minor noble, and William was one of his younger sons. Accordingly, William could not expect any inheritance beyond the title of knight. He went to live with and serve his mother's brother, Patrick, Earl of Salisbury. Although his uncle was killed in an ambush in 1168, and William was taken as a prisoner, he was ransomed by Eleanor of Aquitaine, who had apparently been impressed by his skills.
William soon found that he could make a fortune for himself by traveling around and competing in tournaments (tournaments at that time were not the formalized jousts often depicted in films and Romanticist literature, but were much more violent, dangerous, and disorderly affairs, in which knights would attempt to capture other knights, steal their armour and equipment, and demand ransoms from their families). William's prowess was legendary even his own time. He is said to have competed in over 500 tournaments and never lost once.
William was hired by King Henry II of England, and fought on his behalf in the rebellions led by the kings sons (Richard Lionheart, Geoffrey and John). He is said to be the only man ever to unhorse Richard, when covering Henry's retreat in 1189. William could have killed Richard, but chose not to, merely killing Richard's horse to make the point.
Following Henry's death, later that year, William was welcomed into the court of his one-time enemy, the now King Richard I. Richard also arranged for William to marry the wealthy young heiress Isabel de Clare, daughter of Richard Strongbow, Earl of Pembroke, a title which now befell William and his successors.
During Richard's absence while on crusade and then in prison, William had been part of the regency appointed by the king to govern in his absence, and was part of the resistance that made war on John, when it became clear that he was attempting to usurp the throne.
When Richard died childless in 1189, William supported the succession of John, and once again was welcomed to the court of a one-time adversary and new king. William soon had a falling out with the new king, but in spite of this he would advocate on the side of John against the other barons in the issuance of Magna Carta in 1215.
Following the death of John in 1216, William was made regent for John's nine-year-old son, Henry III. In spite of his advanced age (seventy), William participated directly in wars both against King Louis VIII of France and against rebel barons on behalf of the young king, and in both emerged successful.
He finally died of sickness and old age in 1219. He was accepted into the order of the Knights Templar on his deathbed, and his eldest son (also named William) commissioned a biography of his father.