MOS 87315 When you read the fine print on the paperwork that ordered me to active duty, you see the term “MOS 7315.” MOS stands for Military Occupational Specialty, something that all active duty personnel are assigned. You will have to do some digging because 7315 is no longer an active MOS. However, you will find its description as “a small chemical unit officer”. This MOS essentially means I am knowledgeable in CBR warfare— chemical, biological and radiological. The 8 stands for instructor, which I acquired when I was teaching at the Chemical Corps school at Ft. McClellan, AL. The ramifications of this MOS can start many a conversation. 2 MOS 87315