What Bothers Me about the Latest GDP estimate

The thing that bothers me the most about the latest GDP estimate is not that it was negative although that was surprising. What bothers me is that our experts completely missed the reduction in government spending due to the winding down of the war in Afghanistan. I have read enough economic history books to say that increases in defense spending have been a reliable way of stimulating the overall economy. It worked in World War II in the 40s, Vietnam War in the late 60s, and Reagan years in the 80s. Defense spending had mixed results at stimulating the economy in the 90s with the first Iraq war and in the last decade with the wars in Iraq and Afghanistan. I think there is a very good case to argue that defense spending has historically a larger multiplier effect on GDP growth than all of the ideas to stimulate the economy in the last stimulus package. Even Paul Krugman argued on PBS that a fake alien threat was needed to stimulate the world economy. So how did our experts miss the downside of war buildups?