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