The Treaty of Pähkinäsaari between Sweden and Novgorod. Under the treaty, the Oulu Region remained in Novgorod. The River Oulujoki was the most important route north for Novgorod and the conquered Karelian people, some of whom became permanent residents.
The Kastelli Castle was built on the mouth of the River Oulujoki as a military base to protect Swedish interests against Novgorod. People moved to Oulu from south-western Finland in particular, encouraged, perhaps, by the Swedish authorities. Swedish power was established.
Pietari Bagge established Oulu Castle on the mouth of the River Oulujoki, at a location with previous military fortifications.
The Treaty of Täyssinä between Sweden and Russia. Russia recognised the Swedish title to Lake Oulujärvi and the Oulu Region, for example.