Things like suicide rates are measured in how many people per 100,000 population die in a year. The active duty strength of the army is over half a million troops (including a fluctuating number of activated reservists). The current rate (per 100,000 troops) for the army is 33. In 2009, the rate was 28 per 100,000 troops, versus 25 for 2010. The rate in 2008 was 20, in 2007 it was 19, in 2006 it was 12.8, and for the decade before that it fluctuated between 10 and 13. The suicide rate for the entire U.S. population is about 11 per 100,000.
Despite the growing number of suicides, taking into account the large number of troops suffering combat stress, all the treatment efforts are paying off. Both the army and marines have introduced several programs to identify and treat those at risk for suicide. This effort is linked with the overall program of dealing with combat stress. Because of much reduced death rates (a third of those in Vietnam and World War II), far more troops are spending more time in combat. During World War II it was noted that troops could only take so much combat stress before they developed debilitating mental problems. The military has developed many programs to counteract the stress but nothing that can eliminate it.
It's well known that the suicide rate in the military is linked to stress. For example, back in 2005-6, the U.S. Navy was concerned when the suicide rate among submarine crewmen went to 35 per 100,000. At the time the rest of the U.S. military Army had a rate about a third of that. The suicide rate for submariners was eventually brought down to 20 per 100,000, mainly because the navy identified the causes of the stress and did something about it. But it's always understood that the suicide rate among the 20,000 submarine sailors will be higher, simply because it's more stressful work.
Non-combat stress often creates even higher suicide rates. The Russian military has a rate of 33 suicides per 100,000 troops (that's over 300 suicides). This is declining but not fast enough. Russia is not at war, except for a small force in Chechnya, where they face remnants of separatist and Islamic terrorist groups. The Russian problem is institutionalized brutality of senior troops towards junior troops. This has been a problem since the end of World War II, and the government has been trying to fix it for over a decade now.