President Trump is either a man with extreme chutzpah or a master troll; perhaps a bit of both.
When Trump met recently with Angela Merkel, the German Chancellor, he presented her with a bill for Germany’s “outstanding” share of NATO defense spending. In 2002, the German government pledged to spend 2% of GDP on NATO, but Germany has spent less than this pledged amount. Therefore, Trump had his aides calculate the difference between Germany’s pledged spending and its actual spending. He then presented Merkel with the aggregated difference from 2002, plus interest. The total comes to $374 billion.
German officials have called Trump’s actions “outrageous” and a “provocation” which Merkel ignored.
Given his other interactions with foreign nations, it is debatable whether Trump is a foreign policy genius with some hidden strategy or simply bumbling through his meetings with foreign leaders. While it’s entirely possible it is the former, most people seem to argue the latter.