With its decision to bomb Islamic State militants in Iraq and funnel aid to the fragile Iraqi government in Baghdad, the United States has found itself with a set of strange bedfellows. Russia has been giving outgoing Iraqi Prime Minister Nouri al-Maliki fighter jets for use against the extremists. Tehran has ramped up its military assistance to Baghdad. And in the strangest of bedfellows, Syrian strongman Bashar al-Assad has been carrying out a sustained series of airstrikes against Islamic State targets inside both Iraq and Syria, in some ways doing Washington's work for it.

The unstated and unacknowledged marriage of convenience has left the Obama administration in a bind. The White House heralded this week's destruction of the last of Assad's chemical weapons stockpiles, an achievement that was only possible because he has remained in power long enough to ink the deal and ensure that it was carried out. With senior U.S. policymakers like Secretary of State John Kerry pledging to "destroy" the Islamic State, Washington is effectively gambling that Assad will be willing and able to continue hammering the group. If he were to fall, the militants would have access to an even larger arsenal of powerful weapons. Privately, some lawmakers and military officials concede that the United States needs Assad's help, even if Washington can't ask for it or coordinate its military campaign with him.

There is an enormous price tag for Assad's continued survival, however, and it was laid out in a stark and eye-opening U.N. report Friday. The Syrian civil war that erupted because of Assad's violent attacks on peaceful protesters and has included widespread human-rights abuses by his forces killed at least 191,369 people between March 2011 and April 2014, the report estimated.

But that figure all but certainly understates the number of deaths caused by the war. The report's authors adopted a meticulous, conservative approach, counting only deaths for which they had a full name and the date and location. In a conflict as violent as the Syrian civil war, bereft of stable government institutions and inundated by hyperviolent militias, the true toll is likely significantly higher. "The total 191,369 can be understood as a minimum bound of the number of killings between March 2011 and April 2014," the 25-page report says.

Its authors decline to speculate what the true total might be and note that statistical estimates will be required to determine such a figure. Indeed, the report hints at the enormous difficulties of carrying out such a task. "Well-known individuals who are victims of very public acts of violence, and victims who are killed in large groups tend to attract public attention, and they are therefore likely to be reported to one or more of these sources," the report states in discussing potential bias in its data. "By contrast, single individuals killed quietly in a remote corner of the country tend to be overlooked by media and documentation projects."

Of course, this brutality is unlikely to surprise anyone tracking the conflict, but recent events in Iraq threaten to rejigger the geopolitics of the conflict. Most importantly, the execution of the American journalist James Foley has provided the possible emotional catalyst for a sustained campaign to degrade the Islamic State. "[Islamic State] and the wickedness it represents must be destroyed, and those responsible for this heinous, vicious atrocity will be held accountable," Kerry said earlier this week.

American officials are now contemplating the degree to which they are willing to commit the U.S. military to such a fight. Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, has said that such an effort would in all likelihood require American strikes in Syria as well as Iraq.

The actual U.S. commitment required to achieve the goal of destroying the Islamic State may be much higher. "If destroying ISIL becomes the near-term policy goal ... [that effort] will actually require years, direct military action on both sides of the Iraq/Syria border, tens (if not hundreds) of billions of dollars, and many more than 15,000 troops," Brian Fishman, a military analyst at the New America Foundation, wrote in a widely discussed article this week. "ISIL is an inherently resilient organization -- look how far they have come since getting 'rolled back' during the Surge in 2007 when 150,000 American troops were occupying the country."

On the Damascus side of the Syrian border, the alignment of U.S. interests with Bashar al-Assad's has become all too obvious. Islamic State militants have built up a stronghold in Raqqa province and appear headed for a head-on confrontation with the Syrian army. While Assad has been widely accused of allowing and indeed encouraging the growth of the Islamic State, he has now reached the point where he must soon challenge or contain the group before they can pose a direct challenge to his rule.

And therein lies the dilemma for the Obama. At one point, he might have used the secular Syrian opposition to strike at Islamic State fighters -- and at Assad. But Obama declined to arm more moderate elements of the Syrian opposition, and now he finds himself fighting a psychopathic group of hard-line Islamists on both sides of the Iraq-Syria border.

Can he swallow the bitter pill of allying himself with one mass murderer to take on another? Probably not.

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