New York Times v. United States was a landmark Supreme Court case that reinforced the principle of freedom of the press under the First Amendment. The case arose when the Nixon administration attempted to prevent the publication of the Pentagon Papers, a classified government report detailing the U.S. involvement in Vietnam, arguing that it posed a national security threat. The Supreme Court ruled in favor of the New York Times, emphasizing that prior restraint on publication is unconstitutional except under extreme circumstances, thereby protecting the press's role in informing the public.