European leaders are working to adapt to a new world order set by the Trump administration, which requires allies to take responsibility for their own military security — though not without challenges along the way.

Worried about Russian aggression, some members on NATO’s eastern flank have ramped up spending well above the 2% mark. Poland already is at 5% of GDP, for example. Italy, Portugal and Spain, on the other hand, are yet to hit even the 2% level.