While Harald was king he sought to avenge Magnus' rule over Denmark. Harald Began a war against Sweyn that was battled from 1048 to 1066. Throughout the years he plundered many places, an example of this is when Harald pillaged Jutland in 1048. Eventually he headed out to Norway with a fleet of around 300 ships. Sweyn was ready for an attack as well. When Sweyn didn't show up at the correct time Harald sent half of his troops home. Then Sweyn attacked, and were slaughtered. Harald's army was practically invincible to Sweyn!