Here is the full list of all 13 War of the Vikings achievements.
Revive a squadmate
Win one game as the leader of a squad
Kill 10 saxon squad leaders in a single round
Kill 10 viking squad leaders in a single round
Kill an opponent using a throwing dagger
End a game with at least 10 kills and 0 deaths
Win 10 games in a row
Reach rank 10
Reach rank 20
Reach rank 30
Reach rank 40
Reach rank 50
Reach rank 60