In Sicily, Donald Trump listened attentively during complex G7 debates over trade and climate change, smiled for the cameras, and for the most part refrained from provocative tweets.
In Brussels, he bashed NATO partners for not spending more on defense, shoved the prime minister of Montenegro and renewed his attacks on Germany's trade surplus with the United States.
America's allies witnessed the two sides of Trump on his first foreign trip as U.S. president, a nine-day tour that began with sword dancing in Saudi Arabia and vague pledges in Israel to deliver Middle East peace.
As Trump headed home, European officials were left with mixed feelings: relief that he had been patient enough to listen to their arguments and unsettled by a Jekyll-and-Hyde figure who is still finding his way on the big policy issues.
"It all fits with his strategic ambiguity approach to life," said Julianne Smith of the Centre for a New American Security. "It may do wonders when dealing with adversaries. But it doesn't work when dealing with allies," she said.