The Smith Act of 1940 5 made it a criminal offense for anyone to knowingly or willfully advocate, abet, advise, or teach the duty, necessity, desirability, or propriety of overthrowing the Government of the United States or of any State by force or violence, or for anyone to organize any association which teaches, advises, or encourages such an overthrow, or for anyone to become a member of or to affiliate with any such association. No case involving pros ecution under this law was reviewed by the Supreme Court until in Dennis v. United States 6 it considered the convictions of eleven Communist Party leaders on charges of conspiracy to violate the advocacy and organizing sections of the statute. Chief Justice Vinson's plurality opinion for the Court applied a revised clear and present danger test 7 and concluded that the evil sought to be prevented was serious enough to justify suppression of speech. If, then, this interest may be protected, the literal problem which is presented is what has been meant by the use of the phrase 'clear and present danger' of the utterances bringing about the evil within the power of Congress to punish. Obviously, the words cannot mean that before the Government may act, it must wait until the putsch is about to be executed, the plans have been laid and the signal is awaited. If Government is aware that a group aiming at its overthrow is attempting to indoctrinate its members and to commit them to a course whereby they will strike when the leaders feel the circumstances permit, action by the Government is required. 8 The mere fact that from the period 1945 to 1948 petitioners' activities did not result in an attempt to overthrow the Government by force and violence is of course no answer to the fact that there was a group that was ready to make the attempt. The formation by petitioners of such a highly organized conspiracy, with rigidly disciplined members subject to call when the leaders, these petitioners, felt that the time had come for action, coupled with the inflammable nature of world conditions, similar uprisings in other countries, and the touch-and-go nature of our relations with countries with whom petitioners were in the very least ideologically attuned, convince us that their convictions were justified on this score. 9