If you've ever watched the semi-historic television show Vikings, you know that Rollo is the brother of Viking King Ragnar Lothbruk. Ragnar is a "historically dubious" character, although some of his sons on the television are true historic figures; Rollo is based on the historic Viking leader who besieged Paris in 885-886 and became the first king of Normandy. According to some legends, Rollo was an ancestor of Charlemagne.
On this day in 911, Rollo laid siege to Chartres. As part of the Norman invasion of France, Rollo laid siege to the city but was forced to flee when Charles the Simple managed to get the Franks to charge Rollo's forces. With no real means of escape, Rollo's army soon had to stand their ground and managed to repel the Franks. Thus there was no real winner here, but history records this as a French victory as negotiations led to the Treaty of Saint-Clare-sur-Epte which awarded Normandy to Rollo who had to pledge his vassalage and convert to Catholicism.
Anyway, today is a good time to give a nod to Rollo by posting this cover version of the theme to Vikings, performed by L'Ochestra Cinematique.