The U.S. Navys Summer Pulse 04 exercise, conducted over the last few months, in which seven carrier groups surged out to sea in response to a hypothetical crises, provided an opportunity to see what changes would have to be made for this new strategy to work. The surge strategy is a sharp change from the decades old policy of regular six month cruises (followed by 18 months in port for training and maintenance.) Under the old policy, carriers in port were still considered liable for sea duty in an emergency, but generally did not prepare for it. With the new surge system, ships will spend only about ten percent of their time at sea, rather than the previous 30 percent (the six month cruise plus shorter training cruises.) Under the new system, ships are expected to be as ready as possible for deployment, while in port. This means that supply levels (food, fuel, ammo, spare parts and so on) have to be kept at, or close to, maximum levels at all times. Crew strength has to be kept as close to hundred percent as well. This means that leaves and temporary duty (for training, usually) have to be carefully scheduled in order to keep the maximum number of people on board. This might even lead to the policy of keeping crew size at over 100 percent. Under the old system, you would go to sea on the six month cruise with over 90 percent of your authorized crew size. But during the 18 months in port, the carrier might see a third or more of its crew on leave or away for training.