AMERICAN soldiers, as their recent dispatch of Osama bin Laden demonstrates, may well be the world's best. Unfortunately for their cash-strapped paymaster, they are very expensive. After languishing in the 1980s, military compensation has, since the mid-1990s, steadily outstripped that of civilians (see chart). This month Robert Gates, Barack Obama's outgoing defence secretary, launched a review of Pentagon spending. He warned in a speech on May 24th that pay, pensions and health care would all need to be restructured, or they would crowd out the purchase of vital new weapons.

Military benefits, from subsidised food and education to free college tuition, have traditionally been used to enhance the appeal of a job that involves, at the best of times, limited freedom and frequent moves and, at worst, being killed. But with the exception of the army during the worst years in Iraq, the armed forces consistently meet or exceed their targets for recruitment and retention.

Indeed, Robert Hale, the Pentagon's comptroller, says the department now has the opposite problem: with unemployment around 9%, fewer soldiers are quitting, pushing up costs. Some branches are moving to force people to leave.

The real drivers of military pay and benefits nowadays are political. Democrats and Republicans may disagree violently on how to wage America's wars, but they are unanimous in their gratitude towards the people who fight them. Meanwhile, any proposals that might curb benefits usually run into a powerful and organised lobby for active and retired servicemen. Its umbrella group, the Military Coalition, lists 33 organisations with 5.5m members.

Basic pay is required by law to grow in line with civilian pay. But Congress has consistently added 0.5% to the annual pay rise. Military officers now earn much more than federal civilian employees with the same level of education. And military benefits add up to around 100% of pay, compared with 55% for federal civilian workers. Since 1999 service members have seen their typical out-of-pocket costs for housing eliminated, seen their pensions enriched several times (including a 25% increase) and gained the right to transfer their subsidised college tuition to a child or to their spouse.

But the real budget-buster is health care, which, Mr Gates says, is “eating the Defence Department alive.” Since 2000 its annual health-care bill has shot from $17 billion to $49 billion, and the Congressional Budget Office reckons it will reach $65 billion, or 11% of the defence budget, by 2015.

As well as suffering the usual pressures of medical cost inflation, military benefits have become steadily more generous. A retired soldier pays only $460 a year for family coverage (serving members pay nothing), a sum unchanged since the plan, known as Tricare, began in 1995. Private and federal civilian workers pay $4,000-$5,000. Tricare's cost has also been inflated by absorbing, since 2001, any medical expenses not covered by Medicare for over-65-year-olds. Dealing with all these costs is complicated by the fact that there is no obvious way to put a price on what a soldier does.

Congress seems to be starting to get the message. Three times it ignored George Bush junior's proposal to raise Tricare fees; this year, the Republican-controlled House of Representatives is on the verge of granting Mr Obama's request for a (much more modest) 13% increase. The premium would then grow, though only with inflation rather than the higher health-care inflation rate Mr Obama had asked for. Even if the Senate agrees, the savings will be trivial, at less than $7 billion over five years. But it is a sign of the times that, for the first time in memory, military compensation is no longer untouchable.