With lots of American reserve officers being called up to active duty and sent to work in active duty units, you often find reserve officers working under the command of active duty officers 5-10 years younger. Officer promotions, especially after you reach captain (O-3) come slower in the reserve than in the active duty army. Thats because in the active duty army the rule of up or out (get promoted within a certain amount of time or get retired or sent to the reserves) is applied more vigorously. The older reserve officers, despite their junior rank, bring a large amount of experience with them. Most of these reserve officers end up in staff positions, where they can share their experience with the younger men and women in command. Adult supervision never hurts.