I dont think there was any distinction between Brigadier, Major, Lt General or General in the insiginia. As to how they distinguished the difference in combat I would say they probably knew their own commanders. I doubt that during the heat of battle if somebody with three stars, with or without the cluster was questioned by enlisted men when an order was given. Also if they were anything like most people I believe they would have felt if two Generals were in the same place the one issuing orders would be assumed to hold the higher rank. Just my opinion so take it for what its worth :0)