For the west's masters of war, it's a good time to be in Wales. A military alliance that has struggled for years to explain why it still exists has got a packed agenda for its Newport summit. Nato may not be at the centre of Barack Obama and David Cameron's plans to ramp up intervention in the Middle East and wipe the so-called Islamic state "out of existence". But after 13 years of bloody occupation of Afghanistan and a calamitous intervention in Libya, the western alliance has got an enemy that at last seems to fit its bill. Swinging through the former Soviet republic of Estonia today, the US president declared that Nato was ready to defend Europe from "Russian aggression".