Rommel in my opinion was a very very talented General and had he been running the show instead of Hitler the Germans probably would have won the war, now Rommel given time and a bit of leeway could have hidden these tanks in forests and bunkers out of sight from the air rather close to the beaches which when he gave the order could have sprung forth and decimated the allies due to the fact most of the bombardment on the German positions was on the artillery batteries and the Navy would not have fired on the Germans for fear of hitting the Allies. But as it was had Hitler have realised the tanks when Rommel wanted them right after the landings instead of thinking them a farce and holding them at Calais Rommel again might have inflicted massive casualties on the Allies and successively stalled fer time which would have allowed the German to bring up rienforcements prolonging the war.