OK. Though Advance Wars has many characters with different skills there is one thing that will always stay the same. Follow your characters strengths. CO Powers can turn the tide in any battle, but if they are used ineffectively they are only a waste. You can look at the basic strategies for each character in the game.
Andy[edit]
His CO Powers allow him to keep his units in the field for a much longer period of time, and are great counters to the damage dealing CO Powers of Hawke, Drake, and Olaf. Because of his balanced forces and his healing CO Powers, Andy prefers a large, balanced map with numerous bases, airports, and naval ports.
Max[edit]
Given by its name, he has the Maximum power among all the COs. However beware, Max has its weakness by a lesser attack range and lesser firepower for its indirect units. So it is like Grit but only in a direct unit version. This is probably taken from World War 2's USA where it has a lot of strong units to combat against Germany and later Japan that caused to their defeat. His CO Power is horrible, it can have as nearly as 160% attack power that would totally annihilate foe's unit with +1 movement space. His SCO can have as high as 180% attack power that could destroys a foe. Remember, when powers are used, his indirect units will have a further penalty which decreases his firepower instead. So use Max only if the map requires direct attacking.
Olaf[edit]
His powers should be used very strategically, at a crucial point to either halt the opponents' retreat or advance, allowing Olaf to take the initiative. Olaf's strategies greatly resemble those of the Soviet Army in World War 2, relying on 'General Winter' (a very cold winter with many blizzards) to halt the Nazi Army's advance on Stalingrad and Moscow.
Grit[edit]
In close-quarters, Grit's CO Powers can allow your indirect units to massacre a very large portion of the map (or possibly the entire map if you're playing in a small, enclosed map like Little Island). After using his power, artillery units fire as far (or farther than) other COs' rocket units! Rockets for the price of artillery! You'll find the sound of artillery fire will shortly become your halleluiah chorus. You'll want a good proportion of your army to consist of indirect attacking units such as artillery, rockets and battleships. However, don't let that 20% direct attack penalty scare you; you're still going to need a couple of tanks to clean up what your rockets don't quite finish, or a couple anti-air to cover your rear whenever airports are involved in the match.
Colin[edit]
Colin is best used on maps with lots of properties and with the fund rating set to about 6000-9500 as his SCO Power uses his cash to increase his units’ atk power all the way to horrific amounts with up to a massive 999% atk which would absolutely devastate your foes. Colin's CO Power is useful for earning up cash to deploy his cheap units to flood the enemy, and when the time is right, activate his SCO Power to crush your horrified enemies.
Kanbei[edit]
He has a great troops that are different to Max who has a weakness on indirect units (Weaken power + Less 1 attack range). However, his troops is 20% more expensive. So use Kanbei if the map has lots of city to conquer. His CO power is super, where it decides a winning or a losing battle. This is probably resembles to World War 2's Japanese troops where their morale are high which increases the effectiveness of the troops and able to hold out for long time despite the lack of the resources and its allies were defeated. The SUPER Power is Samurai Spirit. This makes impossible missions come true. I meant, Kanbei's infantries could take on any hit without losing any hp when this power is used and the unit is located on 4 stars defense (Mountains or HQ)
Eagle[edit]
Given by its name, he is the Prince of Air. It's strategy is probably taken from Nazi Germany's Blitzkrieg, which meant lightning war. His CO Power is Lightning Drive and SUPER Power is Lightning Strike. Use Eagle only if the map is mainly airports or you will lose out on his excellent aircraft even though you will still get the second move for all non-capturing units. A good strategy is to get a few bombers, tanks and ranged units, attack, use the Super Power and then attack again, also have a few APCs, landers and transport copters with infantry in, as they will get 2 turns to move, you can set infantry on most or all of the enemy bases and then you will be able to capture a huge amount of enemy buildings.