Russia’s arrival in Syria complicated U.S.-led operations against the Islamic State military group in Syria, which began a year earlier. With few exceptions, the law banned military-to-military cooperation between the United States and Russia unless Russian forces withdraw from Ukraine. (Air Force Tech. Another was that senior U.S. military officials already could consult senior civilian officials at the Pentagon in cases where they ran into any difficulty with the Russians. Air Force Brig.

Source: Washington Post February 23, 2017 18:09 UTC