Does the speed of a unit such as a tank have any modifiers when combat takes place? Speed/maneuverability on the battlefield means that a tank can disengage if a situation is unfavourable and then try to get to a better position to out flank or find a weak point where as if a tank is slow then it is at the mercy of the enemy and can't take the initiative.
It would also add to the strategy of upgrading your engines beyond what is needed just to get to the battlefield.
It would also add to the strategy of upgrading your engines beyond what is needed just to get to the battlefield.