The Norman invasion of Wales began shortly after the Norman conquest of England under William the Conqueror, who believed England to be his birthright. It was not William's intention to invade Wales also, but Welsh attacks under King Gruffudd ap Llywelyn, unifier of Wales, against the Normans in England, beginning in the years prior to the main Norman invasion in 1066, eventually forced William's hand. Initially (1067–1081), the invasion of Wales was not undertaken with the fervor and purpose of the invasion of England. However, a much stronger Norman invasion began in 1081 and by 1094 most of Wales was under the control of William's eldest son, King William II of England. The Welsh greatly disliked the "gratuitously cruel" Normans and by 1101 had regained control of the greater part of their country under the long reign of King Gruffudd ap Cynan, who had been imprisoned by the Normans for twelve years before his escape. Gruffudd had some indirect help from King Magnus III of Norway (Magnus Barefoot) who attacked the Normans briefly off the Isle of Anglesey in Northwest Wales near Ynys Seiriol, killing Hugh of Montgomery, 2nd Earl of Shrewsbury and leaving the Normans depleted and demoralized. Magnus went on to take the Orkney Islands, the Hebrides, and the Isle of Man, islands north of Wales and west and north of Scotland and England, in 1098.