"These are the first American ships home-ported here since Polaris-missile submarines left in the 1970s," US base officials said in a statement from the Defense Department. "Two American Aegis-equipped frigates now call Rota home and two more are scheduled to join them next year," the statement detailed.
The Aegis BMD system is fitted with anti-ballistic missiles capable of hitting targets at short range inside the Earth's atmosphere, and short to intermediate range targets above the atmosphere. In 2008 the Pentagon announced it had succeeded in using the Aegis system to destroy a decaying US intelligence satellite orbiting the Earth.
US military officials said in the press release that as well as having proximity to areas of conflict like Libya, West Africa and the Middle East, ships based in the port "are also closer to the Black Sea that the USS Ross entered in September to reassure NATO allies in the wake of Russia’s annexation of Crimea and its aggression in eastern Ukraine."