On July 19, 2013, General Martin E. Dempsey, Chairman of the Joint Chiefs of Staff, wrote a letter to Sen. Carl Levin detailing the costs of various military options in Syria. Dempsey also explained the purpose of the cost-estimating exercise. "The decision over whether to introduce military force is a political one that our Nation entrusts to its civilian leaders," the general wrote to the Chair of the Senate Armed Serves Committee. "I also understand that you deserve my best military advice on how military force could be used in order to decide whether it should be used." (emphasis in original)

To train and assist the Syrian rebels would cost U.S. taxpayers $500 million, and the costs only increase from there. Gen. Dempsey estimated a no-fly zone will cost "$500 million initially, averaging as much as a billion dollars per month." Establishing a buffer zone where opposition forces could organize and train would require a limited no-fly zone, which, when "coupled with U.S. ground forces would push the costs over one billion per month."

A mission to control chemical weapons in Syria would involve "thousands of special operations forces and other ground forces...Costs could also average well over one billion dollars per month."

Even if the U.S. limits the mission to missile strikes against Syrian targets, the costs would "be in the billions."

But the real unknown is the costs that could accumulate if the civil war deepens, including possibly after Assad's ouster. Dempsey didn’t attempt to estimate the costs to U.S. taxpayers if the U.S. military becomes involved in such circumstances. He did recommend, however, that "we must anticipate and be prepared for the unintended consequences of our actions," and he warned that "we could inadvertently empower extremists or unleash the very chemical weapons we seek to control."

Some have criticized Gen. Dempsey for his candor in laying out the costs and risks of military action in Syria. But we should remember that then-Army Chief of Staff General Eric Shinseki was also criticized for predicting in February 2003 that it would take "several hundred thousand soldiers," to stabilize Iraq after Saddam Hussein's ouster, and, by implication, that the Bush administration’s cost estimates were completely unrealistic. War advocates panned Shinseki’s prediction as "wildly off the mark" but we now know that the general was right, and his critics were wrong.

The costs of reconstruction in Iraq following the fall of Saddam Hussein cost Americans $53 billion from 2003 to 2012, or $15 million dollars a day. That of course doesn’t include the costs of fighting the war itself, including when U.S. troops got caught in the middle of a multisided Iraqi civil war. Total war costs in Iraq already exceed $1.7 trillion, and are expected to climb well beyond $2 trillion. Based on his experience, Stuart Bowen, Inspector General for Iraq Reconstruction, warns that "tens of billions" of dollars would be needed to help Syria begin to recover.

Any estimates focused narrowly on the costs of discrete military operations in Syria are misleading because some accounting must be made of the price that we would pay in the event of a complete collapse of the Syrian regime and a deepening of the civil war there.

In that sense, it is understandable why the American people are particularly skeptical of the proposed intervention in Syria, especially given what they've learned from similar ones over the past decade. It is not that the costs of the operations themselves are exceedingly high. They aren't. It's the operations that come after that could break the bank.