Donald Trump shocked the Western world with his recent comments on NATO. Europe finally seems to be considering a future in which the American nuclear umbrella no longer exists.
The mutual nuclear deterrence between the US and the Soviet Union was one of the main reasons that the Cold War between East and West never became hot. With just a few sentences, Trump has now called this certainty into question. The comment must be the focus of every security policy debate in Germany and Europe from now on, writes Peter Bergen.