President Obama’s decision on deploying more troops to Afghanistan has been complicated by an ugly reality: suicide.

In recent years, the Army has struggled with growing numbers of soldiers who’ve taken their own lives. The numbers spell out the problem starkly. In 2005, the Army’s suicide rate per 100,000 soldiers was 12.7. In 2006, it rose to 15.3. In 2007, 16.8. In 2008 it hit 20.2.

That 2008 figure crossed a disturbing threshold. It was the first time since the Vietnam War era that the suicide rate among soldiers exceeded the rate among their civilian counterparts.

This might not seem remarkable, given the often harsh conditions of military life. But prospective soldiers are screened – in recruitment and in training – for their capacity to cope with those conditions. Going into active duty, their mental health is much better, on average, than that of their civilian peers. Something is deeply amiss when the comparison goes upside down.

The obvious explanation is war. Combat tours in Iraq and Afghanistan run as long as 15 months, and many soldiers don’t get enough down time between deployments. Combat leads to stress disorders and depression as reliably as rain leads to wetness.

Combine that with other problems found in the ranks – marital stress, alcohol abuse, financial difficulties and service injuries – and you’ve got an unusual number of soldiers suffering unusual distress.

Some Army posts, including Fort Lewis, have gone to considerable lengths to assist psychologically wounded veterans. But the numbers remain bleak. As of the end of October, 134 soldiers had taken their lives, compared to 140 through all of 2008. That grim trend line is still headed uphill.

Obama is now deliberating over Gen. Stanley McChrystal’s recommendation that 40,000 more troops be sent to Afghanistan to avert “mission failure.” At the same time, the Pentagon is trying to give military personnel healing time between deployments.

Mathematically, the two goals don’t compute.

Last week, according to The Wall Street Journal, the Joint Chiefs of Staff recommended that Obama not send veterans to Afghanistan unless they have spent at least a year at home in the United States. Under that constraint, the military couldn’t deploy 40,000 more troops anytime soon. One Washington think tank, the Study of War, has concluded that no more than 15,000 soldiers and Marines will have had the requisite year at home to be deployed in the next two months.

Conclusion: The mental health of military personnel is a strategic asset that’s too often been overlooked or given short shrift. Former Defense Secretary Donald Rumsfeld once said that “you go to war with the Army you have.” True. When the Army you have is exhausted and stressed-out from long years of overdeployment, it gets a whole lot harder to go to war.