Russia Forces a U.S. Shift in Northern Syria

Moscow's assertive stance since a Turkish fighter downed a Russian Su-24 in late November has started to effect Washington and Ankara's air operations over Syria. Russian President Vladimir Putin said in a Dec. 17 interview that he sees no prospect of improving ties with Turkey. Putin then dared Turkey to fly over Syrian airspace given the recent Russian deployments of air defense assets in the country. Earlier Dec. 17, Bloomberg reported leaks from unnamed White House officials indicating that the U.S. Air Force had temporarily halted manned aerial missions inside an area the U.S. military designates "Box 4," which is west of the Euphrates River along the Turkish border and also known as the Azaz corridor....