An estimated 150,000 Czech soldiers died in World War I. More than 100,000 Czech volunteers formed the Czechoslovak Legions in Russia, where they fought against the Central Powers and later against Bolshevik troops. Following the collapse of the Austro-Hungarian Empire after World War I, the independent republic of Czechoslovakia was created in 1918. This new country incorporated regions of Bohemia, Moravia, Silesia, Slovakia and the Carpathian Ruthenia (known as the Subcarpathian Rus at the time) with significant German, Hungarian, Polish and Ruthenian speaking minorities. Although Czechoslovakia was a unitary state, it provided what were at the time rather extensive rights to its minorities. However, it did not grant its minorities any territorial political autonomy. The failure to do so resulted in discontent and strong support among some of the minorities for a break from Czechoslovakia. Adolf Hitler took advantage of this opportunity and, supported by Konrad Henlein's Sudeten German Party, gained the largely German speaking Sudetenland (and its substantial Maginot Line like border fortifications), through the 1938 Munich Agreement. Poland annexed the Zaolzie area around Český Těšín. Hungary gained parts of Slovakia and the Subcarpathian Rus as a result of the First Vienna Award in November 1938. The remainders of Slovakia and the Subcarpathian Rus gained greater autonomy, with the state renamed to "Czecho-Slovakia". After Nazi Germany threatened to annex part of Slovakia, allowing the remaining regions to be partitioned by Hungary and Poland, Slovakia chose to maintain its national and territorial integrity, seceding from Czecho-Slovakia in March 1939 and allying itself, as demanded by Germany, with Hitler's coalition. The remaining Czech territory was occupied by Germany, which transformed it into the so-called Protectorate of Bohemia and Moravia. The Protectorate was proclaimed part of the Third Reich and the President and Prime Minister were subordinate to the Nazi Reichsprotektor ("imperial protector"). Subcarpathian Rus declared independence as the Republic of Carpatho-Ukraine on 15 March 1939, but was invaded by Hungary the same day and formally annexed the next day. Approximately 345,000 Czechoslovak citizens, including 277,000 Jews, were killed or executed, while hundreds of thousands of others were sent to prisons and concentration camps or used as forced labour. A Nazi concentration camp existed at Terezín, to the north of Prague. There was Czech resistance to Nazi occupation, both at home and abroad, most notably with the assassination of Nazi leader Reinhard Heydrich in a Prague suburb on 27 May 1942. The Czechoslovak government-in-exile and its army fighting against the Germans were acknowledged by the Allies; Czechoslovak troops fought in the United Kingdom,North Africa, the Middle East and the Soviet Union. The German occupation ended on 9 May 1945, with the arrival of the Soviet and American armies and the Prague uprising. An estimated 140,000 Soviet soldiers died in the fighting for the liberation of Czechoslovakia.
In 1945–1946, almost the entire German minority in Czechoslovakia, about 2.7 million people, were expelled to Germany and Austria. During this time, thousands of Germans were held in prisons and detention camps, or used as forced labour. In the summer of 1945, there were several massacres. The only Germans not expelled were some 250,000, who had been active in the resistance against the Nazis or were considered economically important, though many of these emigrated later. Following a Soviet-organised referendum, the Subcarpathian Rus never returned under Czechoslovak rule, but became part of the Ukrainian Soviet Socialist Republic, as the Zakarpattia Oblast in 1946. Czechoslovakia uneasily tried to play the role of a "bridge" between the West and East. However, the Communist Party of Czechoslovakia rapidly increased in popularity, with a general disillusionment with the West, due to the pre-war Munich Agreement, and a favourable popular attitude towards the Soviet Union, due to the Soviets' role in liberating Czechoslovakia from German rule. In the 1946 elections, the Communists gained 38% of the votes and became the largest party in the Czechoslovak parliament. They formed a coalition government with other parties of the National Front and moved quickly to consolidate power. The decisive step took place in February 1948, during a series of events characterized by Communists as a "revolution" and by anti-Communists as a "takeover", the Communist People's Militias secured control of key locations in Prague, and a new, all-Communist government was formed. For the next 41 years, Czechoslovakia was a Communist state within the Eastern Bloc. This period was marked by a variety of social developments. The Communist government completely nationalized the means of production and established a command economy. The economy grew rapidly during the 1950s and 1960s, but slowed down in the 1970s, with increasing problems during the 1980s. The political climate was highly repressive during the 1950s, including numerous show trials, but became more open and tolerant in the 1960s, culminating in Alexander Dubček's leadership in the 1968 Prague Spring, which tried to create "socialism with a human face" and perhaps even introduce political pluralism. This was forcibly ended by the 21 August 1968 Warsaw Pact invasion. The invasion was followed by a harsh program of "Normalization" in the late 1960s and the 1970s. Until 1989, the political establishment relied on censorship of the opposition, though using more "carrot" than "whip" to secure the populace's passivity. Dissidents published Charter 77 in 1977 and the first of a new wave of protests were seen in 1988. Between 1948 and 1989 more than 250,000 Czechs and Slovaks were sent to prison for "anti-state activities", and over 400,000 emigrated. In November 1989, Czechoslovakia returned to a liberal democracy through the peaceful "Velvet Revolution". However, Slovak national aspirations strengthened and on January 1, 1993, the country peacefully split into the independent Czech Republic and Slovakia. Both countries went through economic reforms and privatisations, with the intention of creating a capitalist economy. This process was largely successful, as in 2006, the Czech Republic was recognised by the World Bank as a "developed country" and in 2009 the Human Development Index ranked it as a nation of "Very High Human Development" From 1991, the Czech Republic, originally as part of Czechoslovakia and now in its own right, has been a member of the Visegrád Group and from 1995, the OECD. The Czech Republic joined NATO on 12 March 1999 and the European Union on 1 May 2004. It held the Presidency of the European Union for the first half of 2009.
