Complex sentence: Hilberman was drafted into the army toward the end of World War II, although he could have been exempt from the draft due to his civilian film work for the army, except that the papers necessary to secure his exemption mysteriously disappeared in an office bottom drawer.
Split into simpler sentences: Hilberman was drafted into the army toward the end of World War II, although he could have been exempt from the draft due to his civilian film work for the army. However, the papers necessary to secure his exemption mysteriously disappeared in an office bottom drawer.