BERLIN, July 4 -- When Donald Trump took to Truth Social on Thursday, the word he reached for was "Ridiculous." His accusation was that the United States was continuing down a "one sided path" while NATO allies failed to reciprocate on defense. Germany, which for decades treated military spending as a political liability its postwar constitution and public opinion combined to constrain, is now on course to hit the alliance's newest benchmark six years ahead of schedule. Friedrich Merz had a pointed reply.

"Germany is doubling its defence budget within four years," the German chancellor told reporters on Friday. "This is the greatest effort we have ever made to strengthen our defence capabilities." He added that Germany would reach the 3....