While Wikileaks informant Chelsea Manning did intelligence work in Iraq in the late aughts during the end of her Bradley days, it’s difficult to gauge her knowledge of current affairs in the troubled state. While there’s nothing unreasonable in suggesting the U.S. combat certain foes with containment strategies and propaganda campaigns rather than through military engagement, there’s no certainty it would work with ISIS. But choking off their illicit income would be a great first step. From her Guardian piece on the topic:

“As a strategy to disrupt the growth of Isis, I suggest focusing on four arenas:

• Counter the narrative in online Isis recruitment videos – including professionally made videos and amateur battle selfies – to avoid, as best as possible, the deliberate propaganda targeting of desperate and disaffected youth. This would rapidly prevent the recruitment of regional and western members.
• Set clear, temporary borders in the region, publicly. This would discourage Isis from taking certain territory where humanitarian crises might be created, or humanitarian efforts impeded.
• Establish an international moratorium on the payment of ransom for hostages, and work in the region to prevent Isis from stealing and taxing historical artifacts and valuable treasures as sources of income, and especially from taking over the oil reserves and refineries in Bayji, Iraq. This would disrupt and prevent Isis from maintaining stable and reliable sources of income.
• Let Isis succeed in setting up a failed ‘state’ – in a contained area and over a long enough period of time to prove itself unpopular and unable to govern. This might begin to discredit the leadership and ideology of Isis for good.

Eventually, if they are properly contained, I believe that Isis will not be able to sustain itself on rapid growth alone, and will begin to fracture internally. The organization will begin to disintegrate into several smaller, uncoordinated entities – ultimately failing in their objective of creating a strong state.”