In addition to the new units, it's worth revealing that Battleships can now launch an indirect attack immediately after moving and Carriers are newly-capable of producing Seaplanes, one of the most powerful aircraft which can strike any unit. Units can also now level-up up to three times for each enemy they destroy, each level gain granting a slight boost in attack and defense.

The most dramatic change in Days of Ruin's gameplay is the much more subtle role of COs. No longer able to turn the tide of battle in an instant, most of their powers lie with granting attack and defense boosts to certain units stationed within a small local affected area. COs can now be loaded into a unit on the battlefield, automatically increasing that unit's rank to Veteran level. Dealing damage within the Command Zone (a small area surrounding your CO's unit) gradually raises the CO's power gauge, but it's quite difficult to fill so don't rely on your superpower to always bail you out of a hairy situation. In fact, the game doesn't even grant you CO abilities until fairly late in the campaign.
All in all, between the new units (including ones that can clear away Fog of War and build temporary air and seaports), the tempered role of COs and varying battle conditions, Advance Wars: Days of Ruin is a more tactical game than its predecessors. Conquering the enemy will require a little more finesse than brute strength. You even have the option of having a CO give you step-by-step strategic advice on how to win each battle in Campaign mode.
