President Barack Obama’s decision to start arming Syria’s rebels has baffled many foreign policy realists who see little reason for the United States to involve themselves in the Middle Eastern country’s civil war. But his seemingly indecisive posture in the conflict may yet stem from a shrewd analysis of American interests in the region.

Daniel W. Drezner writes at Foreign Policy that last week’s announcement — which supposedly followed conclusive evidence of chemical weapons use in Syria although The Washington Post revealed on Saturday that the decision to arm opposition forces was made weeks in advance — “is simply the next iteration of the unspoken, brutally realpolitik policy toward Syria that’s been going on for the past two years,” the goal of which, he argues, “is to ensnare Iran and Hezbollah into a protracted, resource draining civil war, with as minimal costs as possible.”

This policy doesn’t require any course correction… so long as rebels are holding their own or winning. A faltering Assad simply forces Iran et al. into doubling down and committing even more resources. A faltering rebel movement, on the other hand, does require some external support, lest the Iranians actually win the conflict.

Syria’s Bashar Assad is Iran’s only Arab ally and provides it with access to the militant group Hezbollah in Lebanon which is, in turn, an Iranian ally against Israel. Britain’s The Independent newspaper reported on Sunday that Iran was even planning to deploy several thousands of its troops to the country to support Assad’s. Hezbollah fighters also recently joined his army and helped drive rebels out of Qusayr last month, a city on the road from the capital Damascus to Homs, another hotbed of rebel activity.

The opposition, on the other hand, is backed by Sunni powers in the Persian Gulf who regard Iran as their nemesis. Unlike Western countries, which fear (or feared) galvanizing an Islamist insurgency in Syria, Saudi Arabia and Qatar have send weapons into the country, sustaining the rebellion against Assad. They are motivated by not only strategic but sectarian imperatives. The uprising is composed of mostly Sunni Muslims who are Syria’s majority population whereas religious minorities, including Assad’s Alawite tribe, continue to support the regime, if reluctantly, for fear of retribution under a majoritarian successor government.

Such an outcome is probably not desired in Washington DC. Indeed, it doesn’t seem that the Obama Administration envisages a particular outcome in Syria at all. But by giving the rebels a shot in the arm — the “small arms” the United States are expected to send will be of but some help against Assad’s professional army — it does keep Hezbollah and Iran occupied a little while longer, forcing them to commit more resources to the war and preventing them from causing mischief elsewhere.