When William II died on 2 August 1100, Robert was on his return journey from the Crusade and was about to marry a wealthy young bride to raise funds to buy back his duchy. As a result, his brother Henry was able to seize the crown of England for himself. Upon his return, Robert – urged by Flambard and several Anglo-Norman barons – claimed the English crown on the basis of the short-lived agreement of 1087. In 1101, he led an invasion to oust his brother Henry; he landed at Portsmouth with his army but his lack of popular support among the English as well as Robert's own mishandling of the invasion tactics enabled Henry to resist the invasion. Robert was forced by diplomacy to renounce his claim to the English throne in the Treaty of Alton. It is said that Robert was a brilliant field commander but a terrible general in the First Crusade. His government (or misgovernment) of Normandy as well as his failed invasion of England suggests that his military skills were little better than his political skills.