In the coming decades, the United States will face security challenges related to not only the continuing global war on terrorism but also to the growing power-projection capabilities of regional states armed with increasingly potent weapons. In the future global security environment, sea basing (a concept for assembling, equipping, launching, and supporting forces from the sea without reliance on land bases) will be critical to the Navy and Marine Corps' ability to project -- and sustain -- forces ashore. With sea basing, Marine combat power can build up more quickly in a littoral area, and the need to move large amounts of supplies ashore will be minimized. As such, sea basing clearly will be useful in the event of joint forcible entry operations (JFEOs). This monograph documents work done in support of the Navy and Marine Corps' review of JFEOs. It describes the global environment in which such operations might occur, and the role of naval power in that environment. It also considers various options for substituting ships built to commercial standards ("black hulls") for those built to military specifications ("gray hulls"). This work should be of interest to individuals involved in defense policy or military procurement.