The Test Ban Treaty of August 5, 1963, prohibits nuclear weapon tests or other nuclear explosions in the atmosphere, in outer space, or under water, i.e., in the environments where detection from outside the territory of the testing state is possible. Underground nuclear explosions are not prohibited as long as they do not cause radioactive debris to be present outside the territorial limits of the state under whose jurisdiction or control such explosions are conducted. The parties to the treaty also undertake to refrain from “causing, encouraging, or in any way participating in” the carrying out of explosions anywhere which have any of the prohibited effects. The treaty is, as President Kennedy pointed out in his message to the Senate, “the first concrete result of 18 years of effort by the United States to impose limits on the nuclear arms race.” Similarly Lord Home, as he then was, said as Secretary of State for Foreign Affairs of the United Kingdom, that the limited test ban in three environments was “a good thing in itself not only first, because it reduces the danger of pollution of the atmosphere, but, secondly, because it makes the first agreement of substance which we have been able to make with the Russians for a very long time.” Mr. Khrushchev, on his part, praised the treaty as a “document of great international significance” and said that “its conclusion means a major success for all people of goodwill who for many years have been actively fighting for the discontinuance of nuclear tests, for disarmament, for peace and international friendship.” It is stated in the Preamble to the treaty that the parties seek to achieve the discontinuance of all test explosions of nuclear weapons for all time and are determined to continue negotiations to this end.