During the next half-century, Turkmenistan played its designated economic role within the Soviet Union and remained outside the course of major world events. Even the major liberalization movement that shook Russia in the late 1980s had little impact. However, in 1990, the Supreme Soviet of Turkmenistan declared sovereignty as a nationalist response to perceived exploitation by Moscow. Although Turkmenistan was ill-prepared for independence and then-communist leader Saparmurat Niyazov preferred to preserve the Soviet Union, in October 1991, the fragmentation of that entity forced him to call a national referendum that approved independence. On 26 December 1991, the Soviet Union ceased to exist. Niyazov continued as Turkmenistan's chief of state, replacing communism with a unique brand of independent nationalism reinforced by a pervasive cult of personality. A 1994 referendum and legislation in 1999 abolished further requirements for the president to stand for re-election (although in 1992 he completely dominated the only presidential election in which he ran, as he was the only candidate and no one else was allowed to run for the office), making him effectively president for life. During his tenure, Niyazov conducted frequent purges of public officials and abolished organizations deemed threatening. Throughout the post-Soviet era, Turkmenistan has taken a neutral position on almost all international issues. Niyazov eschewed membership in regional organizations such as the Shanghai Cooperation Organisation, and in the late 1990s he maintained relations with the Taliban and its chief opponent in Afghanistan, the Northern Alliance. He offered limited support to the military campaign against the Taliban following the 11 September 2001 attacks. In 2002 an alleged assassination attempt against Niyazov led to a new wave of security restrictions, dismissals of government officials, and restrictions placed on the media. Niyazov accused exiled former foreign minister Boris Shikhmuradov of having planned the attack.