It comes down to this: should the UK use what little international influence it still has to encourage the resumption of international peace talks - and could David Cameron and Philip Hammond bring themselves to champion the cause of the EU as an essential part of the mix? Or would they rather ask the House of Commons to approve RAF bombing raids in Syria, even though they must know full well that a few more bombs - even if they carry "Made in Britain" markings - are unlikely to make a blind bit of difference?
Should the EU fail again in a future crisis, whether economic or humanitarian, the tide will surely turn in the 'Out' campaign's favour. Unless pro-EU campaigners swiftly make a positive case for the future of the EU, and why Britain needs to be a part of it, a 'Brexit' could be a very real prospect by 2017.
If you thought the Suez crisis of 1956 was a long way away, consider that there were joint Russia-China-Iran naval exercises this year, the collapse of the Soviet bloc in 1989 could be considered just a pause and the West versus the world's murkier and more dictatorial states is still a conflict in progress.