1. Iran raised the stakes.

The country said it would soon violate a central tenet of the 2015 nuclear deal — limits on how much nuclear fuel it can produce — unless it gets help from Europe to offset American sanctions. Above, the nuclear enrichment facility in Natanz, south of Tehran, in 2007.

Iran had continued to abide by the terms of the nuclear deal even after President Trump pulled out last year. Now, it appears to be testing whether the other signatories will stick with the White House, which is calling for greater international pressure on Iran.