Americans often assume that insurgency is a modern phenomenon, invented by Mao Zedong and refined by his emulators. The notion permeates official thinking, including Department of Defense definitions and doctrines. In reality, insurgency has existed ever since states and empires began attempting to impose their will on people too weak to resist with conventional military means. Its strategic significance, however, has ebbed and flowed over time.

Authored in 2006, the U.S. Army and Marine Corps' counterinsurgency field manual essentially enshrined counterinsurgency as nation-building in U.S. military doctrine. But in both Iraq and Afghanistan, we learned that this approach required a prodigious effort without commensurate returns. The COIN doctrine's failure in actual practice is due as much to its misguided premises as to any failures in their tactical application.

For the past several years, the widely accepted view among defense analysts had been that counterinsurgency, or COIN, represented the future of U.S. defense planning and operations. Now things have become far less clear. But if COIN is no longer considered the future of U.S. military operations, what definitive lessons, if any, have we learned from its decade of prominence?

Once fashionable within the Washington beltway, counterinsurgency has come under withering criticism, as violence in Afghanistan escalates and the Pentagon tightens its belt. But despite the temptation to avoid future counterinsurgency interventions, contingencies don't always conform to strategic theory. Like it or not, manpower-intensive stability missions have a peculiar way of finding us.

Defense policy analysts and pundits are arguing about whether or not counterinsurgency is dead or alive. The real debate -- the one that risks getting lost in the noise about counterinsurgency's vital signs -- concerns the future of the U.S. Army. As the U.S. military ends its role in Iraq and winds down in Afghanistan, the U.S. Army, alone among the armed services, has no compelling narrative for how it fits into the nation's defense.