Commanding Officers (COs) represent the leaders of the forces of Wars World in Advance Wars. In the game itself, one is chosen at the start of every game (or two, if Tag powers are enabled) and each have their own unique day-to-day abilities, CO Powers and Super CO Powers that affect the game in a variety of ways.
In AWBW, not all COs are necessarily considered to be balanced with one another for competitive play, and are thus divided up into different tiers to reflect their relative power level. This is shown in the Tier List.
CO abilities are usually made of three components - the Day-to-Day ability (or D2D for short) which affects the game passively, and the CO Power (COP) and Super CO Power (SCOP) which have a meter that must be charged up in order to be used. Andy and Adder do not have any day-to-day abilities and Von Bolt does not have a CO Power, but all COs have a Super CO Power.
Day-to-day abilities are permanent and active 100% of the time. They can have various different effects but are most often an increase - or even decrease - in the attack or defence of specific units. For example, all of Jake's units gain +10 attack on Plains, and all of Max's direct units (except footsoldiers) gain +20% attack while his indirect units lose -10% attack. You can check on what the D2D ability is of any CO in a game by mousing over their CO portrait.
CO Powers and especially Super CO Powers have a huge range of effects and can vary in power from a modest combat boost (such as Adder's Sideslip) to a game-swinging power that turns the tide of battle whenever it is used (such as Eagle's Lightning Strike), often - though not always - correlating with how expensive a power is and how long it takes to charge. Every CO Power will give a universal +10% boost to their attack and defense on top of their normal day-to-day abilities and their effects usually last until the start of their next turn.
A CO Power can be activated when smaller portion of the Power Meter (or Charge Meter) is filled, represented in AWBW by a segmented bar under each CO's portrait. Despite their visual appearance on the website, sections of the power meter are often referred to as Stars as a holdover from Advance Wars 2 and Dual Strike, where the CO meter was represented by a row of small and large stars.
Every star is worth 9000 funds at the start of the game. Each additional use of CO Power (including SCOP) increases the value of each star by 20% (1800) up to the tenth usage; after this, it won't increase any further.
Stars on the power meter can be charged in two ways: damage dealt by your units - where you gain meter equal to 50% of the value in damage you inflict - and damage received by your units - where you gain charge equal to 100% of the value of the damage you take, including damage from counterattacks. Damage dealt by missiles launched from Missile Silos and Black Bombs do not count, however, towards either damage dealt or received. Damage dealt by CO Powers directly (such as Olaf's Winter Fury) also does not contribute to meter gain in any way.
The meter cannot be 'overcharged' - if a CO's power meter is full, any further power they gain after this point will simply be wasted. In addition, if a CO's Power is currently active, they cannot gain any CO meter until the power ends.
Keep in mind that while damage calculations do track unit health down to the hundredths, AWBW only keeps track of whole numbers for the purpose of meter calculations. That means that withstanding an attack that does 57% damage and losing 5 HP only adds 50% of the value of the unit to the Charge Meter, not 57%.
The total amount of charge added to the meter during an attack or counterattack can be calculated as:
... where damage dealt and damage received is the integer difference of hit points before and after the attack.
Real unit cost is also factored into the calculation, so COs with cost-affecting powers (namely, Hachi and Colin who have price reductions and Kanbei who has a price increase) will charge their powers more slowly and more quickly, respectively. This also applies for their opponent as well - for example, even though Hachi cannot gain power meter while his COP Barter is active, his opponent will only gain meter from his units at half their usual rate.
Tags are a mechanic that can be enabled where players may take two COs into battle, instead of one. This includes picking the same CO twice - for example, Eagle + Eagle. Tag Breaks (or Dual Strikes) are not present in AWBW - charging up both COs powers to full does not give any option to use both at once, and is in fact generally wasteful as at least some charge will inevitably be lost in this state.
Despite two COs being present, only the day-to-day effects and abilities of the active CO are present at any given time. The active CO may be switched at the end of a player's turn, which can give tag battles a strategic element of using the right CO at the right time to maximise the combination's effectiveness. However, while the effects are limited to that of the primary CO, power bar charging is not; the secondary CO gains power charge as well, at half the rate of the primary CO who still follows the same formula listed above for power charge gain. This present an interesting dynamic for tags - COs with poor or detrimental day-to-day abilities but strong CO Powers can spend most of the battle benched and eventually charge up enough to be able to use their power on a key turn.
The best COs to use as active COs are thus ones who can gain strong incremental advantages using their day-to-day abilities, with less concern than usual about needing to have strong or fast-charging powers to close out games as the partner CO can cover this weakness. Von Bolt is an example of a strong frontliner CO, with the strongest non-broken day-to-day in the game letting him easily shoulder most of the heavy fighting long enough for his secondary to finish charging their SCOP.
Due to the half-rate charging, not all CO Power-reliant COs are necessarily suitable partners, as it can take an excessively long time to charge up their powers otherwise. Thus, good partners for dedicated secondary (or 'backpack') COs have powers that exhibit good cost efficiency for their price, with extra emphasis on SCOPs that have lasting effects such as mass repairs or damage. Andy is an excellent example of a strong Tag CO, as he does not have to worry about lacking a day-to-day while losing none of the passive pressure he exerts by the existence of his Hyper Upgrade.
Using a power in a tag battle is the same as normal and will only increase the COP cost of the active CO. However, whenever a CO's power is active, neither CO may gain any power charge, not even the secondary CO. Switching COs when a power is active will immediately cause the power to end, which can be highly useful to ensure a steady supply of power charge even at the expense of the lasting effects of a SCOP during the opponent's turn.