Navy cargo vessels--collectively known as Afloat Prepositioning Ships Squadron 4, or APSRON 4--are based at Diego Garcia. Among the newest and most advanced ships in the nation's inventory, they are the key component in a force-projection partnership among the Army, Navy, civilian contractors and merchant mariners. The goal of that partnership is to be able to put two armored battalions and two mechanized battalions ashore anywhere in the world within 15 days of notification to do so.