The Great Surprise attends all wars, from the Civil War to the 1991 Gulf War. The Great Surprise is a condition or predisposition that enters into a war's execution so as to make the war more gruesome, expensive and astonishing in its outcome. It is always unforeseen, and it always tailors itself perfectly so as to maximize horror.
In the case of the Civil War, the Great Surprise came from the fact that America's legal infrastructure had matured sufficiently so that patents could be made to stick. Inventors learned that much money could be made by inventing effective weapons. Thus, soldiers trained to wage an 1840's-style Mexican War found themselves facing at close range modern Gatling guns. Body counts of 20,000 per afternoon became common.
In World War I, the Great Surprise was the condition that both sides were equally powerful. So the war, even with its modern weapons, stalemated into something that was long, long, long.
In World War II, the Great Surprise for Germany was that the Kitty Hawk Kite had grown to become the B-29 bomber. The B-29's air raids incinerated cities regularly. Japan's Great Surprise was that somebody found a practical application of the famous E=mc2 equation; Hiroshima was vaporized by a piece of uranium no bigger than a pencil-tip eraser.
Regarding the Vietnam War, the Great Surprise to America was that Vietnam was determined to remain Vietnamese, and had long since learned to repel foreign invaders on a shoestring budget.
Our war-waging president is blind to the existence of the Great Surprise. He assures us that our military bulk, like a mighty tank, will easily bump obstacles out of the road.
Obstacles like Osama.