Across the foreign-policy community, surprise has been expressed that the Obama administration, after several months of eschewing to use American airpower against the forces of the Islamic State of Iraq and Syria (ISIS), ordered strikes this past week. Given the president's last-minute willingness to forego a military operation against Syria this past year, some have raised the question as to whether there is any consistency in terms of the current national-security team's approach to the use of the sword in international affairs.

Upon closer examination, however, there should be no surprise. Generally, the administration is loath to use military force until a certain number of key factors have converged. As in Libya in 2011, the stars aligned to clear away the objections that had already been voiced for months to the utilization of American airpower.

While the United States did not need a United Nations Security Council resolution to take action, there is little international objection to strikes on ISIS. Moscow may be returning to a virtual Cold War status with Washington over the situation in Ukraine, and Tehran has no love for American interference in Middle Eastern affairs, but when it comes to stopping ISIS's advance in the region, there is no daylight between U.S., Russian and Iranian preferences. This is one time when the exercise of U.S. military might does not provoke the usual knee-jerk reaction on the part of the usual suspects.

The fate of Iraqi Yezidis trapped in mountainous areas without access to food or water, and facing the possibility of wholesale slaughter at the hands of ISIS has provided the administration with its "Benghazi"—a localized, definable population that faces an imminent threat requiring U.S. action. Before, the ISIS advance was still being viewed through the lens of the latest iteration of the Sunni-Shia civil war throughout the region (of which other clashes, in Syria and Lebanon, are also facets). The fall of the largely Christian town of Qaraqosh—itself housing many refugees who fled after Mosul fell under ISIS's brand of strict Sharia law—also provided a secondary justification.

There is also the matter of timing. When ISIS first began to challenge the writ of the Nouri al-Maliki government, there was no immediate sense of urgency. Given Maliki's own authoritarian tendencies, his willingness to engage in sectarian preferences, his flirtation with Moscow and the general impression that his administration had, through its own policies, created the conditions that allowed ISIS to spread, there was a belief in Washington that Baghdad ought not to be rescued from its own mistakes. The dispatch of a small number of U.S. advisors was meant to assess the conditions of the Iraqi military and areas where improvements might be made—a mission that was still ongoing at the time airstrikes began. But when it became clear that the security forces of the autonomous government in Kurdistan would not be able to cope—a regime much more reliably pro-American and generally more responsive to Washington's concerns—the calculus shifted.

Finally, and not insignificantly, ISIS possesses no sophisticated air-defense networks and no way to reliably down American aircraft. While no mission is without military risk, using U.S. airpower in Iraq approximated the "low-risk, no casualty" standards that defined the 2011 Libya operation. With the Iraqi military and the Kurdish peshmerga handling matters on the ground, superior U.S. firepower and intelligence capabilities could be deployed from the air to allow Washington to tip the scale on the battlefield.

Absent any (or all) of these factors, it is not likely that Washington would have agreed to undertake military action. Indeed, a greater humanitarian catastrophe across the border in Syria has not pushed the United States to become directly involved—in part, because there is no clear party to aid and the Syrian government still possesses considerable capabilities that could complicate U.S. involvement.

So U.S. action in Iraq does not represent a reversal of policy so much as a continuation of it, and indicates that if the "Libya criteria" can be met in other circumstances, the Obama administration will be prepared to use the U.S. military.

Nikolas K. Gvosdev is a professor of national-security studies at the U.S. Naval War College and a contributing editor at The National Interest.

Image: Flickr/Official U.S. Navy/CC by 2.0