In Advance Wars[edit | edit source]
CO Powers debuted in Advance Wars. Each CO had one power each. Powers built up as units took and inflicted damage. Each CO Power meter was worth a certain amount of damage, with damage sustained being worth half as much as damage inflicted.
As well as a set of unique effects per CO, activating a CO Power also gave every one of that CO's units a 10% boost in firepower and defence. This boost is known as the "standard boost".
In Advance Wars 2: Black Hole Rising[edit | edit source]
CO Powers returned in Advance Wars 2: Black Hole Rising, mostly unchanged from the first game. However, a second tier of power was introduced: the Super CO Power, which were similar to the normal CO Power but stronger. Also, the way how full a CO's bar was measured was changed - rather than a bar that looped around the income and CO portrait, a series of stars was used. This made how much CO power meters were filled much clearer, as each star was worth 9 000G of damage.
The standard boost was changed slightly, and was only worth 10% more defensive strength.
In Advance Wars: Dual Strike[edit | edit source]
Advance Wars: Dual Strike changed the formula slightly again. Rather than making stars represent a monetary value, each unit was given a rating of how many stars it was worth. A third psuedo-tier of powers was also introduced: the Tag Power. A Black Hole idea, Tag Powers allowed two Super CO Powers to be used back-to-back in a single turn. The first CO would initiate the Tag Power and use their Super Power, then play their turn as usual. After they had finished, they would select CO Swap from the menu and each unit would get a second turn, under the effects of the second CO. On top of that, an attack modifier was applied depending on how well the two COs got on in the story.
The standard boost was returned to how it was in Advance Wars.
In Advance Wars: Days of Ruin[edit | edit source]
The entire way COs worked in general was changed for Advance Wars: Days of Ruin. COs can board a unit from the HQ or production property for half of the unit's build cost. Once boarded, the CO Zone will appear around the unit, applying the CO's personal effect as well as a 10% firepower and defense boost to their units within it. The power meter charges based on damage in HP dealt to the enemy when any unit within the zone initiates combat. Each tick represents 6HP and after 30HP, the first bar is filled, expanding the zone by one space. Dealing another 30HP extends the size of the zone by one space again and allows the CO Unit to end its turn to activate the CO Power. In addition to the CO Power effect, Powers also extend the CO Zone to the whole map. Using a CO Power will completely drain the meter and reset the Zone size. The destruction of the CO Unit will also reset the power meter. COs Forsythe and Caulder do not have powers and cannot expand the size of their CO Zones.