We as a country have the single largest economy on the planet, with a 2010 GDP somewhere between $14.4 trillion and $15.1 trillion (let's split the difference and call it $14.75 trillion).
The expected average federal tax rate (Tax receipts/GDP) is expected to be about 14.8%, meaning the federal government would receive about $2.18 trillion in tax collections. If the overall federal tax rate was at the post WW2 average of 18.5%, the federal government would receive about $2.73 trillion, about $550 billion more (deficit reduction!). If we eliminate the war spending, that money can either be not spent at all (more deficit reduction!) or we could spend some of it on badly needed infrastructure projects (creating jobs and putting people to work, thereby reducing or eliminating the need for food stamps - deficit reduction again!) and not spend the rest (even more deficit reduction!).
Links:
http://en.wikipedia.org/wiki/List_of_countries_by_GDP_%28nominal%29http://economix.blogs.nytimes.com/2011/05/31/are-taxes-in-the-u-s-high-or-low/ 
