Harald was only fifteen when the battle of Stiklestad took place

One of the interesting facts about Harald Hardrada is that Harald was only fifteen when the battle of Stiklestad took place. Following a revolt in 1028, Harald's brother Olaf was thrown into exile until early 1030, when he returned to Norway. When Harald learned of Olaf's impending return, he assembled 600 soldiers from the Uplands to meet Olaf and his men when they arrived in Norway's east. Following a warm welcome, Olaf proceeded to build an army and eventually engage in the Battle of Stiklestad on July 29, 1030, in which Harald fought on his brother's side. The battle was part of an attempt to restore Olaf to the Norwegian crown, which had been taken by Cnut the Great of Denmark (Canute).

The battle ended in defeat for the brothers at the hands of Cnut's faithful Norwegians, and Olaf was killed while Harald was severely wounded. Despite this, Harald was noted to have displayed tremendous military skill during the conflict.

The Battle of Stiklestad, fought in 1030, is one of Norway's most renowned engagements. King Olaf II of Norway (láfr Haraldsson) was killed in this fight. During Pope Alexander III's pontificate, the Roman Catholic Church made Olaf a saint in 1164. The battle's historical accuracy is being called into question. According to contemporary reports, the king was assassinated. Olaf was assassinated by his own people, according to the Anglo Saxon Chronicle of 1030. Olaf was killed in an ambush, according to Adam of Bremen in 1070, and Florence of Worcester around 1100. These are the only contemporary sources that mention the king's death.