Command of the sea is the foundation of American national security. Adm. Alfred Thayer Mahan, the greatest strategist in American history, identified it as the core American interest (though he wrote before the war on terrorism began and before the development of nuclear weapons). The United States, he argued, can be threatened only by an enemy naval force that could both invade its territory and curb its access to the oceans. Therefore, the foundation of America's national security, as with Britain's, had to be the command of the sea.Indispensable Sea LanesCommand of the sea guarantees security and trade. Ancient Rome certainly understood as much, focused as they were on controlling Mare Nostrum (or Our Sea, referring to the Mediterranean), which forced North African threats like Carthage to attack Rome on its flanks and ensured access to Egyptian crops. The land routes around the Mediterranean were powerful but slow.