Corruption diverted US-supplied arms into ISIS hands via the black market.

Evidence

Further complicating the situation, Iraqi army training programs were subverted by pervasive corruption and provided arms ending up in the weapons black market, where ISIS can buy them (Kirkpatrick, 2014). Sunni tribal leaders were difficult to recruit as allies in the fight. Some were in regions already occupied by the militants; others feared brutal retaliation if they resisted. — Albert Bandura, Moral Disengagement, 2488

Categorization

• corroborated: 2 independent passages support this claim — Albert Bandura, Moral Disengagement: How People Do Harm…, 2488