The NATO summit at the end of June left Donald Trump happy. The US president hailed the "tremendous" agreement by the military alliance's 32 members to ramp up defense spending to 5% of gross domestic product (GDP) by 2035.

Trump had pressured fellow NATO members to do so for years. However, he reserved his customary ire for one member: Spain.

After vocal opposition from the country's prime minister, Pedro Sanchez, Spain's government found a way out of the 5% commitment by claiming that it could meet its defense obligations by spending much less.

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Trump said the decision was "very terrible" and Spain would be made to "pay twice as much."

Sanchez said the 5% target — which breaks down to 3.5% on defense and 1.5% on related infrastructure — was unreasonable and diverting public spending in such a way could damage the economy.

In the end, Spain secured an agreement with NATO that granted it an effective opt-out. That has raised questions about the extent to which many member nations will ultimately be able to afford the spending pledges they have made.

"The choice to ring-fence and prioritize defense amidst public spending cuts is politically challenging and will need strong public messaging to be accepted by the electorate and indeed across governments in office," Fenella McGerty, senior fellow for defense economics at the International Institute for Strategic Studies (IISS), told........

© Deutsche Welle