Viking raids resumed on England, putting the country and its leadership under strains as severe as they were long sustained. Raids began on a relatively small scale in the 980s but became far more serious in the 990s, and brought the people to their knees in 1009–12, when a large part of the country was devastated by the army of Thorkell the Tall. It remained for Sweyn Forkbeard, king of Denmark, to conquer the kingdom of England in 1013–14, and (after Æthelred's restoration) for his son Cnut to achieve the same in 1015–16.