All that spending's part of our 2% NATO commitment. If we didn't spend it on wars we'd spend it on something else military. Or upset Mr Trump even more.
I very much doubt that all the money that has had to be spent as a result of that 2% comes from the 2% - the human cost of those wars, the destabilisation in the middle east - the need for humanitarian aid, the refugee crisis, the rise in terrorism - and the measures to protect against it, the money being spent (or not) on veterans who have been disabled or traumatised in the line of duty.
the 2% might cover the cost of setting the fire, but it doesn't cover the cost of putting it out.
We chose to go into Iraq, Libya, Syria - Nato didn't make us. Our Parliament voted to do it. JC warned against them all, he voted against them all - he will make different decisions. And those decisions will save lives and money.
And that money can be spent elsewhere. We can make different decisions. We can even make decisions that will upset the POTUS - no matter who they happen to be at the time. Just because we've always spent money doing something does not mean we have to continue doing the same.
And once they've poured the money into infrastructure, public services and jobs then the resulting booming economy will reap higher taxes. People who feel they have more money in their pocket will spend more, so businesses will do better, so more taxes. And they'll have to employ more people to cover their increased business - so more taxes etc etc etc. It's basic Keynesian economic theory. It's the best way to get out of recession. Austerity was a choice - a poor one, that was ideologically not economically motivated. Anyone who worries about the economy as their deciding factor in voting, and votes for more austerity - does not understand economics.
We can choose a different way. The government can choose different priorities to spend on than the one that preceded it.
Yes - I'm sure that's a massive over simplification. But the fact is, well over 100 professional economists (who know a hell of a lot more than I do about these things - and probably a hell of a lot more than everyone else on this thread) took the time to endorse the Corbyn plan. They didn't have to - they did it because they believe - with all their knowledge and expertise - that it is workable.
The money is there - this can be done.