After two years under rhetorical assault from the president, US alliances have somehow held up. This year, however, the constraints on US President Donald Trump's anti-alliance instincts are falling away, and a mix of internal and external pressures are endangering several key alliances at once.
This trend is most visible with respect to Nato. The transatlantic alliance has been a target of Mr Trump's ire for decades. Since taking office, he has berated European leaders, waffled on America's Article 5 commitment to protect allies, and even mused about withdrawing from the pact.