mobile artillery would surely boost the effectiveness of artillery a lot, as if you position your arty closer to the front it means less time for your shell to travel and you could hit moving targets more effectively. Else you need extraordinary intuition and luck to hit a moving target... (I once hit a full, speeding bren carrier with a mortar round on port en bessin but I don't really know how I calculate the entire thing in my mind, I think I "calculate" the speed and position of bren carrier using the engine sound change, and the kill shot is my only shot also)
