Crowds that shop daily in base commissaries and exchanges perhaps are oblivious to a confluence of forces threatening to dismantle their multi-billion dollar resale systems. Thomas C. Shull, chief executive officer of the Army and Air Force Exchange Service (AAFES), is not, which helps to explain his 17 MAR memo proposing a merger of commissaries with exchanges to try to save both. While Department of Defense civilian and military leaders testify that base grocery stores can survive 20 percent higher prices, and that base department stores can weather falling sales, behind the scenes the systems’ top managers are sounding alarms. At risk are the prized discounts on groceries and merchandise the military has enjoyed for decades. Industry sources contend the threats have never been more real, more numerous or potentially more destructive.