Of course Gareth is quite right to point out that Vietnam was Kennedy's war - but then so was the Bay of Pigs, and one way and another Kennedy avoided getting trapped into a Cuban invasion. Perhaps he'd have had the sense to get out of Vietnam in time to avoid catastrophe. Johnson had some good points, but he very clearly didn't have the wisdom to do that.

Perhaps, in the words of a more modern leader closer to home, he didn't have a reverse gear. And any politician who doesn't have a reverse gear is a disaster in the making.