Yeah... I see Cap's involvement more.. behind the scenes. If there is a battle taking place... Cap is already across enemy lines and fighting the greater threat on the other side... not the immediate threat in front of the regular army. So (for example) If he was there on D Day... I would say he should have been preventing Hydra Super weapons from fixing onto the D-Day invasion force... or something like that. Something that doesn't belittle the efforts of the fighting men who stormed the beaches and parachuted into Normandy.... But something fictional, that only he could do, that aided the war effort covertly.