Yes. I'll be very quick.
We need to remember that NATO wasn't started as an organization to do deployed operations, so there are widely divergent views within the alliance on what the nature of NATO operations really ought to be. There has been an enormous amount of reluctance on the part of certain nations to do the deployed side of the house.
Most of our eastern European allies in particular want to focus NATO more on the defence of Europe than anything else, often forgetting that the western border of NATO is somewhere in, probably, Hawaii or Guam. NATO itself has difficulty coming to an agreement on what's right and what's wrong in terms of operations that are optional.
Equally, the UN Security Council, in my view, is only effective in those narrow circumstances where there are no national interests of the “Big Five”. Consequently, it's largely ineffective. Therefore, in many of those circumstances, coalitions of the willing are the only way to move forward.