Yugoslavia, following the death of communist leader Josip Broz Tito in May 1980, the trend of political reform of the communist system occurred along with a trend towards ethnic nationalism and inter-ethnic hostility, especially in Serbia, beginning with the 1986 Memorandum of the Serbian Academy of Sciences and Arts followed by the agenda of Serbian communist leader Slobodan Milošević who aggressively pushed for increased political influence of Serbs in the late 1980s, condemning non-Serb Yugoslav politicians who challenged his agenda as being enemies of Serbs. There was continuing civil strife in Northern Ireland, including the adoption of hunger strikes by Irish Republican Army prisoners seeking the reintroduction of political status. Mikhail Gorbachev became leader of the Soviet Union in 1985, and initiated major reforms to the Soviet Union's government through increasing the rights of expressing political dissent and opening elections to opposition candidates (while maintaining legal dominance of the Communist Party). Gorbachev pursued negotiation with the United States to decrease tensions and eventually end the Cold War. During the Revolutions of 1989, most of the communist governments in Eastern Europe collapsed. The fall of the Berlin Wall in 1989 would be followed in 1990 by the German reunification. The United Kingdom was governed by the Conservative Party under Prime Minister Margaret Thatcher, the first female leader of a Western country. Under her Premiership, the party introduced widespread economic reforms including the privatisation of industries and the de-regulation of stock markets echoing similar reforms of U.S. President Ronald Reagan. She was also a staunch opponent of communism, earning her the nickname The Iron Lady. Poor industrial relations marked the beginning of the decade; the UK miners' strike (1984–85) was a major industrial action affecting the UK coal industry. The strike by the National Union of Mineworkers (NUM) was led by Arthur Scargill, although some NUM members considered it to be unconstitutional and did not observe it. The BBC has referred to the strike as "the most bitter industrial dispute in British history." At its height, the strike involved 142,000 mineworkers, making it the biggest since the 1926 General Strike. In November 1982, Leonid Brezhnev, who had led the Soviet Union since 1964, died. He was followed in quick succession by Yuri Andropov, the former KGB chief, and Konstantin Chernenko, both of whom were in poor health during their short tenures in office. Asia Following the assassination of Park Chung-hee, South Korean