Posner raises an important issue: why do Americans (and persons of other nationalities) grieve so much when American military personnel (or the military personnel of these nations) are killed during military actions, even when those killed had volunteered for military service? In addition to the reason he stresses-the altruism of Americans toward their military personnel- I believe two other factors are important.
Although the pay required to attract volunteers rose after casualties began to appear in large numbers in Iraq, it did not rise by a large amount. Yet even small increases in the probability of losing one's life are valued highly when young persons are asked to take on the risks found in different civilian occupations. When directly applied to military risks, these estimates suggest that if the Iraq war increased the chances of dying to a typical new member of the American military force by one percent per year of service, this would require about a $3000 increase in pay for each year of service for each person in the military. The amount would be considerably higher for those who knew they would be posted into military action in Iraq, and would be higher in general if one percent is lower than the true risk.
The actual increases that have been required to attract volunteers have been much lower than $3,000 per person serving in the military. This suggests that those young men and women who have volunteered are attracted for other reasons than the higher compensation paid to undertake these military risks. One compelling other reason would be patriotism on their part, and a resulting desire to serve their country. Americans feel considerable indebtedness to its military personnel who lose their lives in combat when their enlistments have been due to such non-financial assessments of the risk to their lives from becoming members of the armed forces during wartime. This indebtedness to those killed for volunteering as least in part for patriotic reasons would explain why there is considerable concern and regret over those who die while serving in combat zones. The same concern applies to policemen who are killed in the line of duty because many are assumed also to be serving because of their interest in protecting the public from criminals.
This reflection on the motives for serving shows up in the difference in attitudes toward the usual volunteers for military service, and the attitudes toward "mercenaries". A mercenary is assumed to be serving mainly for monetary reasons rather than for patriotism. For that reason, their deaths causes less concern and mourning on the part of the civilian populations that they are protecting. To be sure, some of the volunteers serving may not have strong patriotic motivation, but they too gain sympathy since it is impossible to tell them from the very patriotic members of military service.
A second explanation for the great concern about those killed in Iraq is that volunteers enlist under the implicit expectation that the military will take appropriate steps to protect those serving in as effective a manner as possible. There is a widespread perception that the war has been fought with inadequate understanding of the enemy, and insufficient protection of American personnel serving in combat-related positions. That would mean the country has let its military personnel down. This belief about inadequate protection of its military enlistees has led to guilt, and the "altruism" that Posner refers to, toward those serving and dying in Iraq while fighting a war that has not been conducted very well.