Does the U.S. need more mercenaries?

Alex Tabarrok asks a provocative question over at Marginal Revolution:

Should we hire more mercenaries today? Our military already has hired more than thirty thousand non-citizens. Why not bypass residency entirely and go straight to Mexico, India and elsewhere to hire soldiers? If outsourcing is good for US firms then surely it is good for the US government. Outsourcing the military has a number of advantages. The supply of labor is nearly limitless and the price is low. Some people will object that quality is low too but if Indians can be trained to do US tax returns they can be trained to fight US wars. ….we are so desperate for troops in the United States that we are forcing old men and women, people who haven’t seen active duty in forty years, back into service. At US wage rates we could easily hire many thousands of Mexicans. Many Mexican noncitizens are already serving honorably in the US military so there is no reason for quality to decline. Mercenarism may seem unusual today but in the 18th century a typical European army contained 20-30 percent foreign troops – mercenarism was the norm. It’s hard to see how the United States has a comparative advantage in military labor so the future may resemble the past more than it does the present.

The funny thing is that the U.S. relies more on mercenaries than Alex may know — the U.S. military has outsourced a lot of its logistical functions in Iraq, for example. According to this Council on Foreign Relations page, for example, the following functions have been at least partially outsourced:

guarding officials, military installations, and supply convoys; training local troops and police forces; providing interrogators, translators, and transcribers; maintaining and repairing vehicles and aircraft, including the guidance and surveillance systems on tanks and helicopters; running logistics operations and supervising supply lines; driving supply trucks that carry fuel and food; providing warehousing and storage facilities; setting up Internet access and maintaining computer systems; preparing meals for the roughly 135,000 U.S. soldiers; cleaning military facilities, including Army bases and offices; washing clothes; and building housing.

Click here and here for more stories on this phenomenon. However, let’s assume Alex’s question was tied specifically to the use of mercenaries for combat as opposed to non-combat operations. Two quick speculations for why mercenaries might not work out:

1) A big reason mercenaries disappeared from the typical European army was the introduction of the levee en masse — and whaddaya know, it turned out that nationalist fervor trumped mercenaries on the battlefield. I think that’s still true today. 2) One of the arguments for why democracies tend to do better in warfighting is that because voters know their fellow citizens will be on the line in combat, they will be much more risk-averse in their attitudes about war than authoritarian states. As a result, they will only engage in wars that are either a) essential to protecting the homeland; or b) they are really likely to win. The use of foreign mercenaries eliminates this risk-aversion from decision-making.

Finally, it’s not clear to me that Alex’s examples of U.S. “mercenaries” are really akin to the Hessians. Offering a citizenship inducement to foreigners joining the military is undeniably offering an additional incentive to enlist — however, is the incentive a purely economic one or, are there identity motivations as well? Furthermore, in a world without a draft, what is the difference between offering greater monetary compensation to U.S. citizens interested in enlisting and offering similar economic incentives to foreigners interested in becoming Americans? UPDATE: One clarification: I don’t think that linking citizenship to enlistment is necessarily a bad idea — I’m just not sure it qualifies as what Tabarrok thinks of as mercenarism.