All military organizations, from the largest to the smallest are composed of 4 areas. I call these, the X-functions.
X-1. Command Staff and Administration. The command staff is responsible for creating strategy, and creating tasking for the entire unit. The administration is responsible for documenting, and providing administrative support.
X-2. Intelligence. Intelligence is responsible for all aspects of intelligence gathering and counter-intelligence operations. The information they provide is used by the X-1 to create strategy and create tasking orders.
X-3. Operations. Operations is responsible for the organization of operational units, training, and carrying out the tasks assigned from X-1. Operations works closely will all of the X-functions to successfully complete the tasking orders.
X-4. Supply. Supply, as the name implies is responsible for maintaining, inventory, and securing supplies.
Although there are other functions within these X-functions these are the major tasks.