Duke Guillaume "Longue Epee" (William Longsword) I was born about 893 in Normandie, Neustria. He died on 17 Dec 942 in France. He was ambushed and assassinated by servants of Theobald of Bolois and Arnulf of Flanders on the island of Picquigny.

He sought continually to expand his territories either by conquest or by exacting new lands from the French king for the price of homage. In 939 he allied himself with Hugh the Great in the revolt against King Louis IV; through the mediation of the pope, the war ended, and Louis renewed William's investiture of Normandy (940). William, however, continued his territorial ambitions, especially northward. Drawn to a conference on an island in the Somme River, he was assassinated on the orders of the Count of Flanders, Arnulf I.