President Putin’s deployment of troops in two separatist Ukrainian regions has nearly shut the door on diplomacy and intensified a showdown over European security.

Russia has demanded security guarantees that U.S. and NATO officials cannot accept, but there could still be room for building a sustainable dialogue on European security.

The European Union and the United Kingdom came to a last-minute trade deal on Christmas Eve, narrowly averting the hardest of all potential Brexits. But major uncertainty remains.

A changing climate and growing competition for resources is raising tensions among Arctic nations.

With this major U.S.-Russia nuclear arms control agreement set to expire next year, Washington should coordinate with Moscow for a New START treaty extension to allow for further negotiations and the…