In 946 King Haakon I of Norway went north, and set Tryggve to defend Viken against his enemies in the south.
He also gave him all that he could reconquer of land in the area which the summer before, King Haakon had subjected to payment of taxes.
King Haakon was mortally wounded at the Battle of Fitjar in an engagement with Eirik’s sons.
After Haakon's death, Harald Greycloak, third son of Eirik Bloodaxe, jointly with his brothers became kings of Norway.
Tryggve's son, Olaf Tryggvason, later became king of Norway, and his daughter Ingeborg Tryggvasdotter married Ragnvald Ulfsson, the Jarl of Västergötland and later the ruler of Staraja Ladoga.