When we recently set out for meetings in London, Berlin and Brussels on improving transatlantic links on atrocity prevention, foremost in our minds was concern about the dramatic return over the past 18 months of first-tier international security challenges. The rise of ISIS against the backdrop of civil war and humanitarian catastrophe in Syria, the new adventurism of the Russia of Vladimir Putin, and the daunting challenge of the Iranian nuclear program combine to take up a lot of space in the in-boxes of senior policymakers in North America and Europe.