Reality Check: Is Donald Trump right on Nato's funding boost?
The claim: Speaking in Poland, US President Donald Trump said: "My administration has demanded that all members of Nato finally meet their full and fair financial obligation. As a result of this insistence, billions of dollars more have begun to pour into Nato."
Reality Check verdict: President Trump is correct to say billions of dollars more are being spent on defence by Nato allies. But it's not really down to him. The increase began before he took office - after the annexation of Crimea, perceived military threats from Russia, and the rise of so-called Islamic State.
Nato defence spending is on the rise - of that there is no doubt.
The latest statistics show that European Nato countries and Canada (in other words, all member states apart for the US) have spent or will spend an extra $45.8bn (£35.3bn) in the three years from 2015 to 2017, compared to 2014 spending figures.
This year is forecast to see an annual real increase of 4.3%, the largest in this period.
Mr Trump says "people are shocked" by this. He implies that it is only happening because his administration has demanded action.
That is not the case.
The pivotal year was 2014, well before Mr Trump was a candidate let alone a president. It was the year which saw the annexation of Crimea by Russia, increased Russian military activity close to Nato's eastern borders, and - to the south - the declaration of a caliphate by IS.
Geopolitical change helped persuade Nato countries that they had to reverse a decline in defence spending. The United States had been urging them to do that for years.
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At a Nato summit in Wales the same year, Nato leaders pledged to meet, within a decade, the target of spending 2% of their national GDP on defence.
Last year, only five Nato countries met the 2% pledge - US, UK, Greece, Poland and Estonia. Romania has joined them this year, and Latvia and Lithuania are expected to do so in 2018.
Other countries are still some way short of the 2% target - Germany for example, which has been a frequent target for Mr Trump's criticism, will spend only just over 1.2% of GDP on defence this year.
It's also important to remember that a lot of this money isn't "pouring into Nato" itself - on the other hand, national defence spending obviously strengthens the alliance in general.
So is any of it down to Mr Trump? He has certainly been far more vociferous than any previous president that Nato allies should do more to pay their way.
The United States spends more on defence as a percentage of GDP than any other Nato country, and far more as an absolute amount than all the rest of them put together.
But if anything, the effect of Mr Trump's rhetoric has been to add a little more urgency to a decision that had already been taken.
When the Nato Secretary-General Jens Stoltenberg was asked about the Trump administration stance last week, he said: "I welcome the focus of the President on increased defence spending. At the same time it's important to understand that this is implementation of a decision we all made together."
That sounds like a diplomatic way of saying that Mr Trump cannot take all the credit.