Units are organized as historically as possible, therefore one regiment size is not same for UK and for Serbia, but also its not same by default moral, endurance etc. All those things affect outcomes of combats and battles. Besides classical attributes, AoT will have numerous attributes for units that affect them in any activity.
Status of some unit on one hex wont be just its existence on that hex and bonuses of terrain and features, but also what activity it performs on that hex.
So, besides classical moving and attacking, there will be fortification, forceful reconnaissance, fake attacks, support to other troops, reserve position for troops, battle formations for moving and attacking, decisive defense, ambushes, night attacks, fake surrendering etc.
Units can cross map hex by hex or numerous hexes, depending on own attributes and attributes of the terrain, terrain features, props, weather conditions, depending on other units movement, actions of the enemy units etc.
Also, they can be moved in certain formations, which affects their speed and combat readiness.
Unlike the classic turn based strategies, and just modes for attack and defense, AoT has different modes in which the unit can be placed on how to behave in different situations.
Also, the unit itself can be “decomposed” into three sub-continent – wings (left and right) and center, which can take away or add “power” (easiest comparison would be like shields in space simulations). Therefore, the attack and defense can focus in different directions – for example, units next to each other can form a joint attack or support each other etc.
Time of day
Early morning is favorite time for attack, as enemy soldiers are tired or sleeping. Night attacks were dangerous for both attacker and defender. Calculate when and how to attack, because it all counts and affects all units.
Great War started in late summer, with hot weather and sunshine. It went through rainstorms of autumn toward snowy winter and then to snow melting, mud and floods of spring. And then it just went again through all kinds of weather for next 4 years. Use weather in your advantage against enemy, because otherwise enemy will do it against you!