I would bomb vast swathes of the countryside around Germany, essentially creating a new No-Man's Land. I would then have the infantry build deep and wide trenches surrounding all of Germany. I would then send ground troops over in raids, often signaling with a loud whistle or "[i]CHAAARGGHEEE!!![/i]" so that the Germans know when to start shooting at us. I'd also make sure to have miscommunications with the bombers so that they occasionally do a run on American troops. What do you mean that's a stupid and entirely unfeasible way to win a war?