In total, incidents involving sexual assault in which the children of service members are victims occur hundreds of times each year, data the Defense Department provided ... show. The figures offer greater insight into the sexual abuse of children committed by service members, a problem of uncertain scale due to a lack of transparency into the military's legal proceedings. With more than 1 million military dependents, the number of cases appears statistically small. An AP investigation ... found more inmates are in military prisons for child sex crimes than for any other offense. But the military's opaque justice system keeps the public from knowing the full extent of their crimes or how much time they spend behind bars. Responding to AP's findings, three Democratic senators have urged Defense Secretary Ash Carter to lift what they called the military justice system's "cloak of secrecy" and make records from sex-crimes trials readily accessible. The senators also raised another concern. Child sex-assault cases are not included in the Defense Department's annual report to Congress on sexual assaults, which focuses primarily on adult-on-adult incidents, they said. The senators ... told Carter in a Dec. 8 letter they are concerned the department may be underestimating how many sexual assaults are occurring in the military.