Olaf is the Commander-In-Chief of Blue Moon and a major character in the Advance Wars series. He first appears as an antagonist in the first game before turning good and joining forces with the other Wars World nations to stop the threat of Black Hole.
Olaf's backstory is different in the first two Advance Wars games. In Advance Wars, it is stated that he was the former commander-in-chief of Orange Star before leaving them to join Blue Moon. However, in Advance Wars 2: Black Hole Rising, it is stated that he was born and raised in Blue Moon. It is possible that Olaf was born in Blue Moon and later left to join Orange Star before defecting back to Blue Moon.
In Advance Wars, Olaf is tricked into declaring war on Orange Star by a clone of Orange Star's CO Andy who impersonated the real Andy and led an attack on the Blue Moon forces. Taking advantage of the situation, Olaf declares war on Orange Star and uses it as an opportunity to invade the nation and conquer more land for Blue Moon. However, after it is revealed that he was deceived, he and the rest of Blue Moon team up with the other forces to defeat Black Hole.
In Advance Wars 2: Black Hole Rising, Black Hole forces under the command of Lash invade Blue Moon and raze Olaf's home town in the process. However, Olaf and his forces manages to repel Lash and her troops, forcing them to retreat.
In Advance Wa: Dual Strike, Olaf has little role in the main campaign of the game, having stayed in Macro Land to help his country recover. However, a clone of him created by Black Hole appears in one of the later missions to fight the Allied Nations COs.
Olaf is shown to be incredibly greedy. In the first game, he is only concerned with land and power. He is also shown to be a rather incompetent commander in the first game. He forgets to fuel his air units, and uses his Battleships to fend off Submarine attacks, leaving his base wide open for attack.
As time goes on, however, Olaf grows to become a responsible leader and it's shown he actually does care for his men. He is also shown to be an excellent strategist in later games.