When Donald Trump won the US election he did so with the isolationist slogan of "America First", leading many to declare German Chancellor Angela Merkel as the new leader of the free world.



Her pivotal role in global politics could be seen clearly on the White House call sheet during Mr Trump's first few months in office - she was one of the world leaders he spoke to most frequently and she also paid the new president a visit in March 2017.



President Trump's tone towards Mrs Merkel has changed significantly since he took office. In 2015, he took to Twitter to describe her as the "person who is ruining Germany" after Time magazine picked her as their person of the year.



The German leader clearly noticed Mr Trump's disparaging comments, saying at their joint press conference that she's "always said it's much, much better to talk to one another and not about one another".



The meeting appeared amicable enough - albeit with one eye-catching moment of awkwardness - but some reports suggested Mrs Merkel was unimpressed with Mr Trump's command of policy details.



The pair have met several times and spoken on the phone regularly since that first meeting, but there has been a more adversarial tone to Mr Trump's comments on Germany recently.



On immigration, Mr Trump tweeted: "The people of Germany are turning against their leadership as migration is rocking the already tenuous Berlin coalition."



On Nato and trade, he tweeted: "Presidents have been trying unsuccessfully for years to get Germany and other rich Nato Nations to pay more toward their protection from Russia. They pay only a fraction of their cost. The U.S. pays tens of Billions of Dollars too much to subsidize Europe, and loses Big on Trade!"



At the latest Nato summit in July, Mr Trump accused Germany of being "totally controlled by Russia" because it imports "so much of its energy" from the country and has a new pipeline planned. Mrs Merkel responded by saying Germany "can make our own policies and make our own decisions".



While Mr Trump was right that Germany imports most of its gas from Russia, gas makes up less than 20% of its overall energy mix, according to BBC Reality Check.