What we don’t know is killing American soldiers. This isn’t a statement regarding military strategies, circumspect intelligence, or Washington’s unpredictable political winds about war funding.

It’s about what happens inside the mind of a returning soldier, after the revelry of joyous homecomings evolve into the relative monotony of civilian life. Some adapt well, while others never completely return from battle, haunted by their memories, guilt and fears.

There is a name for this condition: post-traumatic stress disorder. We know what it can do: drive returning soldiers to self-destruction or suicide, the last resort for coping with themselves. What isn’t known is why, how it’s stopped or prevented, or why some servicemen and servicewomen are more susceptible to its effects.

Tyler Curtis, an Iraq veteran from Livermore Falls, had all the signs of PTSD. He was bored by his work as a truck mechanic, inexplicably violent in his recreation and brimming with grief. These were harbingers of his suicide on Thanksgiving morning, a story that reverberates in small towns across the nation.

There’s the “Marlboro Marine,” Lance Cpl. James Blake Miller from rural eastern Kentucky, whose battle-hardened visage and dangling cigarette – captured by an embedded photographer following a battle in Fallujah – made the unknown soldier into an icon.

He is home now, sometimes. His struggles with PTSD have ended his marriage, caused serious substance abuse and suicidal thoughts. The photographer, Luis Sinco of the Los Angeles Times, has now intervened into Miller’s life in an attempt to save it.

Miller’s postwar struggles, like those of Tyler Curtis, are as emblematic of warfare as any iconic imagery. PTSD has been linked to increased suicides, substance abuse, homelessness and domestic “interpersonal problems,” to use U.S. Army parlance.

Yet so much about it remains unknown. Only in August did an Army study confirm what was suspected since as early as 2003: suicides among active-duty personnel was reaching its peak. Two weeks ago, the Journal of the American Medical Association reported that symptoms of PTSD take months to appear.

(The study authors, from the Walter Reed Army Institute of Research, also indicated the official comprehension of PTSD among returning veterans was grossly underestimated.)

And only on Nov. 5 was federal legislation targeting soldier suicides enacted; the bill – named for Pvt. Joshua Omvig of Grundy Center, Iowa, who killed himself in 2005 – makes mental health screening, treatment and suicide prevention a greater priority for the Veterans Administration.

It’s taken the United States too long to awaken to this warfare impact on the homefront. Only the ultimate sacrifices from soldiers such as Curtis and Omvig, and struggles of Miller and thousands of others, have finally pushed these issues to the surface. If an enemy were this successful in harming our military, we would strike back twice as hard.

PTSD deserves this same fierce courtesy.