28 September – On this day

The Battle of Tinchebray was fought on this day in 1106, in the town of Tinchebray, Normandy, between an invading force led by King Henry I of England, and his older brother Robert Curthose, the Duke of Normandy.

The previous year Henry had invaded Normandy, taking Bayeux and Caen. He was forced to break off his campaign owing to political problems. With these settled, he returned to Normandy in the spring of 1106. After quickly taking the fortified abbey of Saint-Pierre sur Dives, Henry turned south and besieged the castle of Tinchebray, on a hill above the town. Tinchebray was held by William, Count of Mortain, who was one of the few important Norman barons still loyal to Robert. Duke Robert then brought up his forces to break the siege, and, after some unsuccessful negotiations, decided that a battle in the open was his best option.

Henry’s army was organized into three groups (sometimes called battles). The main two were commanded by Ranulf of Bayeux, Robert de Beaumont, 1st Earl of Leicester, and William de Warenne, 2nd Earl of Surrey. In addition he had a reserve, commanded by Elias I of Maine, out of sight on the flank. Also on Henry’s side were Alan IV, Duke of Brittany, William, Count of Évreux, Ralph of Tosny, Robert of Montfort, and Robert of Grandmesil. On Robert Curthose’s side were William, Count of Mortain, and Robert of Bellême, 3rd Earl of Shrewsbury.

The battle itself only lasted an hour. Notably, Henry ordered much of his force of knights to dismount, as he did himself: unusual for Norman battle tactics, infantry played a decisive role. The Count of Évreux charged the front line, comprising troops of Bayeux, Avranches and the Cotentin. The intervention of Henry’s reserve proved decisive. Most of Robert’s army was captured or killed. Besides Robert himself, those captured include Edgar Atheling (uncle of Henry’s wife), and William, count of Mortain. Robert de Bellême, commanding the Duke’s rear guard, turned his back on the duke and led the retreat saving himself from capture or death. Most of the prisoners were released, but Robert Curthose and William of Mortain were to spend the rest of their lives in captivity. But Robert Curthose had a legitimate son, William Clito, whose claims to the dukedom of Normandy led to several rebellions that continued through the rest of Henry’s reign.