In theory, the idea of national service–making all young people donate a year or two to serve the country–sounds great. It has been endorsed by liberal and conservative luminaries alike. So why hasn’t it happened? Put another way: Why hasn’t the draft been revived since it expired in 1973?

Part of the obvious reason is that Americans are intensely individualistic and resist forced labor even at the government’s behest unless there is some pressing national emergency. There was indeed such an emergency during World War II and the height of the Cold War–but there isn’t now. That is not to say that we don’t face threats, but we have found since the 1970s that we have no trouble filling the military’s ranks with high-quality volunteers.

That has not stopped various thinkers from coming out with national service schemes. The military writer Tom Ricks has a particularly inventive approach on the New York Times op-ed page today. He  understands that there is no way the military could possibly incorporate four million 18-year-olds every year; there are only 1.4 million active-duty personnel in the entire U.S. armed forces. So he proposes that some of the 18-year-olds could choose 18 months of military service that would not involve the possibility of combat: “These conscripts would not be deployed but could perform tasks currently outsourced at great cost to the Pentagon: paperwork, painting barracks, mowing lawns, driving generals around, and generally doing lower-skills tasks so professional soldiers don’t have to.” As for the rest, they could “perform civilian national service for a slightly longer period and equally low pay — teaching in low-income areas, cleaning parks, rebuilding crumbling infrastructure, or aiding the elderly.”

Leave aside the high costs of this plan–Ricks says that all of the kids in question would qualify for free or partially free college tuition. How can we afford that at a time when entitlements are already bankrupting us?

The real problem is that his plan would not address the biggest issue raised by advocates of a draft–the need for fairness so that the risk of combat is not borne by less than one percent of the population. Under the Ricks plan, combat would still be limited to the same volunteers who serve today; nobody would suggest that a teenager who does clerical work in the Pentagon is serving his country in the same way as a teenager who carries an M-4 and walks a foot patrol in Helmand Province. Ricks thinks his plan would “make Americans think more carefully before going to war. Imagine the savings — in blood, tears and national treasure — if we had thought twice about whether we really wanted to invade Iraq.”

But it would have no such effect. To achieve what Ricks wants, the military, now contracting in size, would have to grow considerably and come to rely on conscripts who didn’t want to serve and who would push down the quality of the force. That is something few uniformed leaders would want to see and Congress would never pay for. So national service remains a nice idea–but one that is simply unworkable and unaffordable.