Islamic militant upset about the carnage occurring in Syria. With a month left to the inauguration, the issue Trump and of course, Obama, could face, might be Russian retaliation against Turkey.
Turkey is a NATO state and any attack upon Turkey automatically by the organization agreement, compels the NATO members to defend that state under attack. So far, Trump has been accused of mysteriously cozy relations with Russia, even to the extent that he has denied Russian involvement in the hacking of the Clinton campaign and the DNC.
Below is link to twitter storyline on the latter news story:Tweets about russian ambassador