In 1987, Thatcher visited the Soviet Union, which signified to Powell a "radical transformation which is in progress in both the foreign policy and the defence policy of the United Kingdom". In a speech in the Commons on 7 April, Powell claimed the nuclear hypothesis had been shaken by two events. The first was the Strategic Defense Initiative or "Star Wars": "Star wars raised the terrible prospect that there might be an effective means of neutralising the inter-continental ballistic missile, whereby the two great giants who held what had become to be seen as the balance of terror would contract out of the game altogether: the deterrent would be switched off by the invulnerability of the two providers of the mutual terror".