A string of stunning victories by ISIS, a violent Sunni jihadist group in Iraq, has refocused international attention on this volatile Gulf nation.

The group, which has historical ties with al-Qaeda, surprised many observers last week when it conquered the cities of Mosul and Tikrit, sending Iraqi soldiers and citizens fleeing for safety.

ISIS has threatened to take the capital, Baghdad, which has in turn prompted Prime Minister Nouri al-Maliki to encourage Iraqis to take up arms against the group. Like Syria, the result of this showdown could be a civil war that draws in combatants from neighbouring countries and elsewhere.

Here’s a look at the key players in this escalating drama.