WASHINGTON—A cornerstone of the expanded U.S. military campaign against Islamic State militants will be reliance on U.S.-trained local forces to confront the group head on.
But the U.S. has a poor track record of taking or keeping control in areas such as Iraq and Libya for extended periods, experiences that underscore the risks of depending on moderate rebels in Syria and state security forces in Iraq.
Relying on local forces and eschewing the use of American combat troops has become a favorite strategy of PresidentBarack Obama as a way to reduce the risk of being dragged into a protracted foreign conflict. But some defense officials and experts say that approach also can heighten the risk of failure.
In Iraq, Libya, Afghanistan and elsewhere, results have been mixed at best in U.S. efforts to push local forces to the forefront of fights against extremists. U.S. military campaigns conducted with little or no local ground support—such as those in Pakistan and Yemen—have met with some success but have lasted for years. Success, officials and experts say, is especially difficult when American troops are prohibited from serving alongside local units on the front lines or without a yearslong U.S. presence to train, advise and mentor the partner forces.