On 29 July 1030, King Olaf Haraldsson [Olaf II] was defeated and slain at the Battle of Stiklestad.

King Olaf had been briefly exiled to Novgorod [in modern day Russia] by the Danes and returned in 1030 to reclaim his throne. Thus, the Battle of Stiklestad between King Olaf against a large army of Norwegian farmers involved both politics and religion as Olaf desired to unite Norway under his rule and to Christianize his subjects. Indeed the battle cry of Olaf’s army was reportedly, Fram! Fram! Kristmenn, Krossmenn, kongsmenn or “Forward, forward, Christ’s men, Cross men, king’s men!”

After Olaf’s death, his body was buried in secret and moved to St. Klement’s Church in Trondheim one year later. When his body was unburied, it was discovered to be incorrupt. This was perceived even by Olaf’s enemies as a miracle and contributed both to Olaf’s reputation for holiness and to the further Christianization of the Norwegians.

Olaf would eventually become the patron saint of Norway, the Rex Perpertuus Norvegiae, and on the site of his death was constructed a church. The Nidaros Cathedral was constructed on the site of his burial and is now the location of his body.

The Battle of Stiklestad is seen by historians as marking the end of the Viking period and the beginning of the medieval period of Norway. Each year the pageant Spelet om Helag Olav is performed during the week leading up to St Olaf’s day on July 29. This pageant attracts about 20,000 visitors.

Wikipedia article on St. Olaf – also contains the propers for the Mass of the Feast of St. Olaf