On this day, 28th of July 938, Thankmar, eldest son of King Henry the Fowler (919-936) died from a spear run through his back whilst he was seeking refuge in the chapel of Eresburg castle. This ends the first rebellion against King Otto, later Emperor Otto the Great, who messes up most of his first years in office.Thankmar’s great misfortune was his choice of mother. He was the son of King Henry’s first wife Hatheburg of Merseburg, a rich heiress from Saxony. When Henry first met her, he was – at least according to the chronicler Widukind, so “enticed by her beauty and the usefulness of her inherited wealth” that he married her on the spot. That was rash, very rash. Thing is, he did not meet Hatheburg at a debutante ball or at a dinner party in her parent’s house. No, he found her in a convent where she was about to become a nun. As a prospective nun, she could only marry under dispensation from at least a bishop. Blinded by passion, Henry somehow forgot to put the application in the post and, very much to Thankmar’s chagrin, no dispensation had ever been forthcoming.The lack of dispensation was a bit of a scandal, but nobody really challenged the son of the duke of Saxony. The illegality of the marriage only became an issue after Henry the Fowler’s two older brothers had died and Henry suddenly became the future duke of Saxony. Hatheburg may have been a rich heiress, but was she a rich enough heiress for the future duke of Saxony? Hatheburg had brought a sizeable dowry, the city and county of Merseburg, but there were other, more politically valuable prizes around.And so, Henry started to burn for another, even better endowed beauty, Mathilda of Ringelheim. Mathilda was top of the tree Saxon nobility being a descendant of Widukind, the enemy of Charlemagne and Saxon folk hero (and despicable coward, but let’s just leave that aside). Her family, the Immedingers were a clan of important Saxon counts and also related to another large clan, the Billunger. Hence much more suitable for Henry, future duke of Saxony.Hatheburg marriage was swiftly declared null and void, she returned to her convent and her dowry, Merseburg, was casually added to the ducal estate. Poor Thankmar suddenly dropped down from oldest son and future, future duke of Saxony to landless bastard. In 919 Henry “the Fowler” rose even further and was elected king of East Francia (~Germany) a crown he passed on to Thankmar’s younger half-brother Otto in 936, disregarding any inheritance claims of Thankmar or Otto’s other brothers.Otto had already proceeded to make a number of very powerful enemies in his first year in office. To tip the boat over completely he now alienated Thankmar. The Southern March of Saxony, an important border county had become vacant. Thankmar believed himself entitled to this post. Not only was he the son of the previous king but also Otto had awarded Merseburg, which was Thankmar’s mother’s inheritance after all, to someone else. So as compensation it would only be fair to award Thankmar the March. However, Otto decided against Thankmar and installed Gero, the brother of the previous incumbent as Markgraf. Putting Gero in charge of the Saxon March is when Thankmar loses it. Being the oldest son and having to forsake the crown and now not even getting any position in line with his rank was just too much. Too much not just for him but also for a lot of other Saxon nobles disgruntled by Otto’s treatment of his mother Mathilda, the elevation of Herman Billung to military leader against the Wends and the judgement against duke Eberhard of Franconia. Thankmar and his companions go into open rebellion. They besiege the castle of Belecke where Otto’s brother Henry was holed up at the time. The castle falls and Henry is captured. Thankmar sends Henry down to Eberhard who puts him in a presumably comfortable jail cell in one of his castles.Meanwhile Thankmar and his forces move on to the Eresburg, one of the largest and best defended Saxon castles. Otto’s army follows him there and besieges the castle. Thankmar’s troops lose confidence in their leader and open the gates. Otto’s troops storm in and even though Thankmar throws down his weapons as a sign of unconditional surrender and flees into the castle chapel a soldier runs him through the back with a lance. Otto publicly lamented his valiant if ill advised brother’s death as would be expected of a ruler in the 10th century, though his true feelings will never be known.