Story highlights John McTernan: Brexit proves international organizations are vulnerable

A weakened NATO threatens everyone, McTernan says

(CNN) NATO has a big problem. And it's not President-elect Donald Trump. In the end, the alliance knows how to talk to him and it knows how to influence the security apparatus that sits round any president. No, the real challenge for NATO can be summed up in one word: Brexit.

It's not that Brexit in any way weakens the commitment of British politicians to NATO. Far from it. They have been vehemently -- and sincerely -- committing to continued defense cooperation. The problem is what the Brexit vote proved to the rest of the world: Longstanding international organizations that do not renew their popular mandate are vulnerable.

But there is one big difference between the European Union and NATO. While Brexit is in reality little more than a self-inflicted wound that only makes Britain poorer, a weakened NATO threatens everyone.

Russian President Vladimir Putin understands this. There's been a lot of talk recently about his moving of missiles into Kaliningrad. When he does so, he is doing two things.

On one hand, he is probing defenses, just as he does when Russian submarines enter Swedish waters or Russian jets enter British airspace. On the other, and more significantly, he is opening another front in his information war.

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