Doctrines often guide chief executive’s foreign policy decision-making. The Bush Doctrine assumed the right of anticipatory self-defense and that preventive war was justified when a perceived threat to the United States existed. The Iraq War was a result of the Bush Doctrine. Saddam Hussein’s Iraq was viewed as a threat and preemptive war was necessary. Therefore, the U.S. military overthrew the regime and replaced it with another.
The most widely cited doctrine, the Monroe Doctrine, posited that the Americas were in the American sphere of influence and force would be used to keep it free of external actors. Both the Monroe and Bush Doctrines rationalized when it was prudent to use hard power to achieve objectives. While the Monroe and Bush Doctrines relied on projections of force that depended largely on realist assumptions, the Obama Doctrine, as it evolves, uses realism but also relies on pragmatic assessments and humanitarian criteria to determine when the United States can and should intervene.
Essentially, under Obama, the U.S. will rely on soft power and other tools to avoid direct American intervention into troubled regions of the world. These efforts will be aided by an assessment of situations on the ground as they evolve. However, when situations reach the point that American intervention might be necessary the U.S. will intervene multilaterally.