pointed out that the doctrine was not credible in the face of "less-than-total challenges" such as the Soviet intervention in the 1956 Hungarian Revolution, and that whatever credibility it might have had diminished steadily as Soviet strategic power grew. Furthermore, it theoretically provided the Soviet Union with an incentive to strike first to disarm the United States. The Hungarian Revolution involved a matter internal to the Eastern Bloc, so it is unclear whether any sort of conventional military response would have been undertaken regardless. "New" New Look The refusal of the United States to act to prevent the defeat of France by the communist-led Viet Minh at the Battle of Dien Bien Phu, just four months after the Dulles speech, highlighted the political difficulties Eisenhower faced in balancing interference in Asia with his determination to keep the U.S. out of a "hot war". His refusal to intervene using air strikes – a tactic that he decided would have been ineffective in the scenario of Dien Bien Phu – led instead to a third option: a threat of nuclear strikes against strategic Chinese targets, in line with "Massive Retaliation". This was approved on May 26, on the condition that both congress and U.S. allies supported it. This tactic could not be relied upon to secure US interests in every case however. Defense planners, therefore, began shaping a "new" New Look marked by emphasis on strategic "sufficiency," not superiority; on tactical nuclear weapons to fight "limited wars;" and on standing forces as opposed to reserves. The emphasis was still primarily on nuclear weapons and the justification was still that of economy, but a shift toward what would later be called "flexible response" had begun. The new approach was embodied in NSC5440 (approved as NSC5501 on January 7, 1955), finalized in December 1954, which stated: According to historian Campbell Craig: Notes Further reading Bowie, Robert R. and Richard H. Immerman, Waging Peace: How Eisenhower Shaped an Enduring Cold War Strategy Oxford, New York: Oxford University Press, 1997. Dockrill, Saki. Eisenhower’s New-Look National Security Policy, 1953-61 New York (1996). Hammond, Paul Y. Organizing for Defense, Princeton, NJ: Princeton University Press, 1961. Head, Richard G. and Ervin J. Rokke (eds.), American Defense Policy (3rd ed.), Baltimore: Johns Hopkins University Press 1975. Kintner, William R. Peace and the Strategy Conflict, New York: Frederick A. Praeger, 1967. Millis, Walter ed. American Military Thought, Indianapolis: Bobbs-Merrill Co., 1966.