In USE, the combat system is integrated, so that each unit can move (using some activation points that are consumed based on the available factory or industrial points) 10 and 8 hex for tanks (including mechanized units) and the rest such as infantry, respectively. Each means that each unit is moving and fighting at the same time. The is typically done when the unit is performing mobile attacks individually. I always like to think about the real basis of one rule so that I can understand better the rule itself but also I can become more embedded into the game. For this particular case, the rule has good real basis. For example, one combat unit when it is fighting tend to advance with a lower speed than a unit that is not facing resistance. Here, when fighting you have to pay mobile points so that the maximum number of hex you can move is decreased. It has sense.
In other games, you have to move all the units and after that you have to initiate the attack phase. This is not happening here. You move one unit and attack with that unit. Where is then the synchronization of attacks you can expect in real-world battles?
There is another type of attack that can be done only one time per turn and can involve up to three units that are adjacent to an enemy unit. This type of attack is coordinated so that you can increase the chanced for that particular offensive. The drawback is that you do not have the opportunity to exploit a successfully offensive such as doing a mobile attack.
The ground units represent armies. Yes, it is a big unit. The German army is represented using less than 30 or 40 counters, including garrison armies. For example, the entire famous 6th Army is one counter. It has good points and less good points. The good ones is that, at this large scale (the game simulates the entire second world war) you can move each turn all your units in a relatively small time. It may allow you to focus on the strategy itself, rather than in the dynamics of the game. However, it has a small drawback. Most of the combats or battles may end without “losses” or may result on the partial damage (counter is flipped down) or be completely destroyed. There is not small sub-units or steps a unit may loose before it is entirely removed from the map. For example, other games of similar scale such as The Supreme Commander or Totaler Krieg include corps so that a large Army may be subdivided into corps when facing loses or even due to strategy reasons. I like the current game as it is but as house rules, I’m curious to see what will happen if we are able to combine the Army/Corps size of units with the innovative combat dynamics of USE.