This week in one apparently wanton yank, he ripped one of those cords by announcing a plan to withdraw nearly 12,000 troops from Germany. This thin green thread of forces, woven through Germany's historic towns, rolling fields and dense forests, has for three generations helped ensure peace in Europe, embodying an unbreakable commitment between the former foes.
The relationship now though, particularly if Trump is reelected later this year, is in freefall, destination unknown.
His decision, if his tweets have been correctly divined, seems to be to punish Germany.
"Germany pays Russia billions of dollars a year for Energy, and we are supposed to protect Germany from Russia. What's that all about?" Trump wrote in one post.
"Also, Germany is very delinquent in their 2% fee to NATO. We are therefore moving some troops out of Germany!"
His undiplomatic data grenades were tossed out in a few moments in the middle of the night, but it could take years to undo the damage German official fears it will inflict on the military alliance.
The head of the German parliament's foreign relations committee, Norbert Roettgen, replied on Twitter Wednesday, saying, "Instead of strengthening #NATO it is going to weaken the alliance. The US's military clout will not increase, but decrease in relation to Russia and the Near & Middle East."
Bavaria's state governor Markus Soeder, whose region hosts several US bases, also criticized Trump: "Unfortunately this seriously damages German-American relations. A military benefit cannot be seen. It weakens NATO and the U.S.A. itself."
Little surprise, then, that the Kremlin is gleefully exploiting Europe's consternation, with spokesperson Dmitry Peskov telling CNN: "We never hid that [we think] the less American solders there are on the European continent the calmer it is in Europe."
Trump is the gift that keeps on giving for the Kremlin: his unpredictability, while often a pain, for them is continual grist for their propaganda mill.
It has taken America's 45th president almost four self-serving and destructive years to reach this point, but in pulling the trigger on withdrawing troops from Germany, one-third of the total stationed in the country, he has signaled an end to what Franklin D. Roosevelt, America's 32nd president, conceived as a post-World War II order based on common interest and collective aspirations.
Roosevelt and other leaders of his generation witnessed the worst of times as the great powers collided, propelled by a few evil self-possessed men; assuming Trump is not completely ignorant, he has chosen to ignore this obvious fact.
The problem for NATO and America's other allies is that there seems little that can hold Trump back from his impulses. Secretary of Defense Mark Esper echoed the President's words saying, "Germany is the wealthiest country in Europe. Germany can and should pay more to its defense."
This argument will ring hollow in the cavernous halls at NATO HQ in Brussels leafy suburbs, wh