Steven Erlanger

Two big powers supporting different factions in the Syrian civil war clashed with each other Tuesday when Turkish fighter jets shot down a Russian warplane that Turkey said had strayed into its airspace.

France and Belgium moved aggressively to strengthen the hand of their security forces, pushing Europe more deeply into a debate that has raged in the U.S. since Sept. 11, 2001: how to balance counterterrorism efforts and civil liberties.

The man in the black balaclava who seems to have beheaded several foreign hostages in Islamic State videos has been identified by British security services as Mohammed Emwazi, a British citizen from London.