The level of responsibility the commander of a force is willing to entrust to individual soldiers has varied wildly throughout history. With modern weapons, a single soldier can kill or suppress many times his own number. From around the Franco-Prussian War to World War 2, the old military class in Europe changed their ideas about conscription, service, and professionalism in armies. The peasantry would not necessarily cower in cover unable to be rooted out, a teacher from Birmingham could be taught and impressed by his role as a low level CO, and so on.
These changes could be taken to their logical extreme with droids, who do not cost significantly extra to be imparted with additional "training". Indeed, the amount of information given to a single droid may as well be arbitrary (with, at least, modern SDcard technology). Given that droids have no self-preservation instinct on an individual level, their minds can be wiped if captured with no ethical boundaries. Indeed, a self-destruct "coring" could be standard).
The groups of droids (hitherto "squads") themselves would keep note of how long they might last under hypothetical attack. This would enable any potential reserve squads whether they could halt the enemy advance, or whether they should vacate the area in preparation of a full enemy offensive.
Rules like this one would enable battle command to be almost entirely decentralised, nearly to the point of requiring only a few commanders or even one. Obviously, the minutia would have to be worked out for each droid type, but the rules of at least third generation warfare would remain roughly the same.
The commander could assign major objectives, but the individual flow of droids into an area and terrain would dictate their tactics, which they would work out on the field. The commander could also be removed from the defence of all but the most innovative attacks, allowing himself to concentrate on the strategic aspects of his work. Logistics, the other important subject for any war, is one prone to automation also.
I'm just going to come up with some rules, and discuss what their implications might be. At some other stage, I might write about what an individual droid should do if it is cut off from communications. But for the most part, these are written with at least occasional communications from other droids.
If sufficient reserves can be mounted to hold off an enemy attack, send the reserves and hold the line. However, if such reserves cannot be mounted for any reason, due to distance or lack of troops or being 'reserved' for another operation, begin a soft withdrawal action.
If participating in a soft withdrawal action, move reserves away from the point of attack, and consider strengthening flanks. The formations under attack should attempt to slow the advance for as long as possible.
If there is a salient, attempt to close it at the farthest reaches possible. Try to do it when the enemy's supply chain is most disrupted.
For time when no attacks are forthcoming, attack lightly to avoid casualties and supply waste. This hides preparations for a proper breakthrough, and allows lightly defended areas to be captured.
If squads are too dispersed, consider moving up reserves or retreating to a narrower field of battle.
Supplies should be moved up with reserves.
And so on. You'll notice that a lot of these are rules taught to officers (at some stage or another). However, all droids can be well trained officers (in training and knowledge) while being able to be subservient to one another without drama.
The end result would hopefully look as fluid as a tide that rolls around rocks on the shore. That would be cool, right?