Prophet Proud Prophet was a series of war games played out by various American military officials. The simulation revealed MAD made the use of nuclear weapons virtually impossible without total nuclear annihilation, regardless of how nuclear weapons were implemented in war plans. These results essentially ruled out the possibility of a limited nuclear strike, as every time this was attempted, it resulted in a complete expenditure of nuclear weapons by both the United States and USSR. Proud Prophet marked a shift in American strategy; following Proud Prophet, American rhetoric of strategies that involved the use of nuclear weapons dissipated and American war plans were changed to emphasize the use of conventional forces. TTAPS Study In 1983, a group of researchers including Carl Sagan released the TTAPS study (named for the respective initials of the authors), which predicted that the large scale use of nuclear weapons would cause a “nuclear winter”. The study predicted that the debris burned in nuclear bombings would be lifted into the atmosphere and diminish sunlight worldwide, thus reducing world temperatures by “-15° to -25°C”. These findings led to theory that MAD would still occur with many fewer weapons than were possessed by either the United States or USSR at the height of the Cold War. As such, nuclear winter was used as an argument for significant reduction of nuclear weapons since MAD would occur anyway. Post-Cold War After the fall of the Soviet Union, the Russian Federation emerged as a sovereign entity encompassing most of the territory of the former USSR. Relations between the United States and Russia were, at least for a time, less tense than they had been with the Soviet Union. While MAD has become less applicable for the US and Russia, it has been argued as a factor behind Israel's acquisition of nuclear weapons. Similarly, diplomats have warned that Japan may be pressured to nuclearize by the presence of North Korean nuclear weapons. The ability to launch a nuclear attack against an enemy city is a relevant deterrent strategy for these powers. The administration of US President George W. Bush withdrew from the Anti-Ballistic Missile Treaty in June 2002, claiming that the limited national missile defense system which they proposed to build was designed only to prevent nuclear blackmail by a state with limited nuclear capability and was not planned to alter the nuclear posture between Russia and the United States. While