BAGHDAD — In the steamy Baghdad night, sweat poured down the faces of the Iraqi teens as they marched around a school courtyard, training for battle against the Islamic State group. This is summer camp in Iraq, set up by the country’s largest paramilitary force after Iraq’s top Shiite cleric issued an edict calling on students as young as middle-school age to use their summer vacations to prepare to fight the Sunni extremists. Dressed in military fatigues, 15-year-old Asam Riad was among the dozens of youths doing high-knee marches, his chest puffed out to try to appear as tall as the older cadets. “We’ve been called to defend the nation,” the scrawny boy asserted, his voice cracking as he vowed to join the Popular Mobilization Forces, the government-sanctioned umbrella group of mostly Shiite militias. “I am not scared because my brothers are fighting alongside me.” With dozens of such camps around the country, hundreds of students have gone through the training though it is impossible to say how many went on to fight the Sunni extremists since those who do so go independently. This summer, The Associated Press saw over a dozen armed boys on the front line in western Anbar province, including some as young as 10.