US President Donald Trump has offered both candid praise and unabashed criticism of Germany and its policies. From calling German Chancellor Angela Merkel "possibly the greatest world leader" to describing her open-door refugee policy as a "catastrophic mistake," here are his most memorable quotes regarding Germany.

"Germany's like sitting back silent, collecting money and making a fortune with probably the greatest leader in the world today, Merkel," Trump said in a 2015 interview with US news magazine Time.

"The Germans are bad, very bad ... Look at the millions of cars they sell in the US. Terrible. We'll stop that," Trump said during a NATO leaders summit, according to German news magazine Der Spiegel, which cited sources at the alliance's meeting.

"As far as wiretapping, I guess, by - you know - [the Obama] administration, at least we have something in common, perhaps," Trump said in March during a press conference with Merkel. He was referring to his unproven allegations that ex-President Barack Obama tapped his phone. There was widespread anger in Germany in 2013 when it was revealed the US National Security Agency tapped Merkel's phone.

"I think she made one very catastrophic mistake and that was taking all of these illegals (sic), you know taking all of the people from wherever they come from," Trump said in a joint interview published by German daily Bild and British newspaper The Times, referring to Merkel's open-door policy for refugees fleeing war and persecution.

"Despite what you have heard from the fake news, I had a great meeting with German Chancellor Angela Merkel. Nevertheless, Germany owes vast sums of money to NATO and the United States must be paid more for the powerful, and very expensive, defense it provides to Germany," Trump said in a two-tweet statement after meeting with Merkel for the first time in March 2017.

"The people of Germany are turning against their leadership as migration is rocking the already tenuous Berlin coalition," Trump tweeted in the midst of a row within the German goverment. He went on to claim that: "Crime in Germany is way up. Big mistake made all over Europe in allowing millions of people in who have so strongly and violently changed their culture!"

In late 2014, with the war in Syria approaching its fourth year and Islamic State making gains in the north of the country, the exodus of Syrians intensified. At the same time, others were fleeing violence and poverty in countries such as Iraq, Afghanistan, Eritrea, Somalia, Niger and Kosovo.

Vast numbers of Syrian refugees had been gathering in border-town camps in neighboring Turkey, Lebanon and Jordan since 2011. By 2015, with the camps full to bursting and residents often unable to find work or educate their children, more and more people decided to seek asylum further afield.

In 2015 an estimated 1.5 million people made their way on foot from Greece towards western Europe via the "Balkan route". The Schengen Agreement, which allows passport-free travel within much of the EU, was called into question as refugees headed towards the wealthier European nations.

Tens of thousands of refugees were also attempting the perilous journey across the Mediterranean on overcrowded boats. In April 2015, 800 people of various nationalities drowned when a boat traveling from Libya capsized off the Italian coast. This was to be just one of many similar tragedies - by the end of the year, nearly 4,000 refugees were reported to have died attempting the crossing.

Countries along the EU's external border struggled to cope with the sheer number of arrivals. Fences were erected in Hungary, Slovenia, Macedonia and Austria. Asylum laws were tightened and several Schengen area countries introduced temporary border controls.

Critics of German Chancellor Angela Merkel's "open-door" refugee policy claimed it had made the situation worse by encouraging more people to embark on the dangerous journey to Europe. By September 2016, Germany had also introduced temporary checks on its border with Austria.

In early 2016, the EU and Turkey signed an agreement under which refugees arriving in Greece could be sent back to Turkey. The deal has been criticized by human rights groups and came under new strain following a vote by the European Parliament in November to freeze talks on Turkey's potential accession to the EU.

With anti-immigration sentiment in Europe growing, governments are still struggling to reach a consensus on how to handle the continuing refugee crisis. Attempts to introduce quotas for the distribution of refugees among EU member states have largely failed. Conflicts in the Middle East and elsewhere show no signs coming to an end, and the death toll from refugee sea crossings is on the rise.

US President Donald Trump welcomes Montenegro to the military alliance by appearing to shove Prime Minister Dusko Markovic in order to secure a front row berth. Montenegro will formally join NATO next month, although it may already feel pressured to increase its military spending, which currently stands at 1.6 percent of GDP.

The president was invited to unveil NATO's new 9/11 memorial. However, instead of using his speech to play up unity, Trump scolded allies for owing "massive amounts of money" to the US and NATO. Members have set a 2 percent of GDP defense spending "guideline," although the contributions are supposed to be voluntary.

Trump's 10-minute tirade on defense spending appeared to be greeted with snickering and eye-rolling. An illustration of America's new standing in the world?

Leaked comments obtained by German media reveal that Trump told European leaders that Germany was being unfair with its trade arrangements and decried its surplus. "The Germans are bad, very bad," German weekly Der Spiegel quoted Trump as saying. "Look at the millions of cars they sell in the US. Terrible! We'll stop that."

Trump met with France's newly elected president, Emmanuel Macron, at the US ambassador's Brussels residence. As a life-long businessman, Trump's handshakes are seen as one of his key power moves. Palms dried and jaws clenched, Macron didn't appear prepared to grant him that victory as the leaders embarked on what's been coined "the world's longest handshake."

British Prime Minister Theresa May is reported to have voiced her anger and dismay after US officials leaked details over the identity of the Manchester suicide bomber. The leak led British authorities to halt intelligence-sharing with the US for around 24 hours. The breech also comes just weeks after Trump himself divulged secret intelligence to senior Russian emissaries.

If Trump had sought to assure allies of his commitment to NATO, neglecting to affirm Article 5 of the North Atlantic Treaty - which stipulates that members treat an attack against one ally as an attack against all - wouldn't have helped. Perhaps surprisingly, however, the president did mention the Russian threat on NATO's eastern border.