The 14th century, in particular, the reign of the Czech king Charles IV (1316–1378), who also became the King of Italy, King of the Romans and Holy Roman Emperor, is considered the Golden Age of Czech history. Of particular significance was the founding of Charles University in Prague in 1348, Charles Bridge, Charles Square. Much of Prague Castle and the cathedral of Saint Vitus in Gothic style were completed during his reign. He unified Brandenburg (until 1415), Lusatia (until 1635), and Silesia (until 1742) under the Czech crown. The Black Death, which had raged in Europe from 1347 to 1352, decimated the Kingdom of Bohemia in 1380, killing about 10% of the population.
By the end of the 14th century the so-called Bohemian (Czech) Reformation began. The religious and social reformer Jan Hus formed a reform movement later named after him. Although Hus was named a heretic and burnt in Constance in 1415, his followers seceded from the Catholic Church and in the Hussite Wars (1419–1434) defeated five crusades organized against them by the Holy Roman Emperor Sigismund. Petr Chelčický continued with the Czech (Bohemian) Hussite Reformation movement. During the next two centuries, 90% of the inhabitants became adherents of the Hussite Christian movement.
After 1526 Bohemia came increasingly under Habsburg control as the Habsburgs became first the elected and then in 1627 the hereditary rulers of Bohemia. Between 1583–1611 Prague was the official seat of the Holy Roman Emperor Rudolf II and his court.
The Defenestration of Prague and subsequent revolt against the Habsburgs in 1618 marked the start of the Thirty Years' War, which quickly spread throughout Central Europe. In 1620, the rebellion in Bohemia was crushed at the Battle of White Mountain, and the ties between Bohemia and the Habsburgs' hereditary lands in Austria were strengthened.
The period following 1620 to the late 18th century, has often been called colloquially the "Dark Age". The population of the Czech lands declined by a third through the expulsion of Czech Protestants as well as the war, disease and famine. In 1679–1680 the Czech lands faced a devastating plague and an uprising of serfs.
The reigns of Maria Theresa of Austria and her son Joseph II, Holy Roman Emperor and co-regent from 1765, were characterized by enlightened absolutism. In 1742, most of Silesia (except the southernmost area), at that time the possession of the Bohemian crown, was seized by King Frederick II of Prussia in the Silesian Wars. In 1757 the Prussians invaded Bohemia and after the Battle of Prague (1757) occupied the city. More than one quarter of Prague was destroyed and St. Vitus Cathedral also suffered heavy damage. However, soon after, at the Battle of Kolín Frederick was defeated and had to leave Prague and retreat from Bohemia. In 1770 and 1771 Great Famine killed about one tenth of the Czech population, or 250,000 inhabitants, and radicalized the countryside leading to peasant uprisings.
An estimated 1.4 million Czech soldiers fought in World War I, of whom some 150,000 died. More than 90,000 Czech volunteers formed the Czechoslovak Legions in France, Italy and Russia, where they fought against the Central Powers and later against Bolshevik troops. In 1918, during the collapse of the Habsburg Empire at the end of World War I, the independent republic of Czechoslovakia, which joined the winning Allied powers, was created. This new country incorporated the Bohemian Crown (Bohemia, Moravia and Silesia) and parts of the Kingdom of Hungary (Slovakia and the Carpathian Ruthenia) 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 and remained the only democracy in this part of Europe in the interwar period. The effects of the Great Depression including high unemployment and massive propaganda from Nazi Germany, however, resulted in discontent and strong support among ethnic Germans for a break from Czechoslovakia.
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, because of the pre-war Munich Agreement, and a favourable popular attitude towards the Soviet Union, because of 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. A significant change came in 1948 with coup d'état by the Communist Party. The Communist People's Militias secured control of key locations in Prague, and a single party government was formed.
Burning Soviet tank in Prague during the Soviet-led invasion of 1968 after a Czechoslovak attempt for liberalization of the regime.
From 1948 until 1989, Czechoslovakia was a Communist state within the Eastern Bloc. This period is characterized by lagging behind the West in almost every aspect of social and economic development. The political climate was highly repressive during the 1950s, but became more open and tolerant in the late 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 invasion by all Warsaw Pact member countries with the exception of Romania and Albania on 21 August 1968.
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. 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, 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 1 January 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 market economy.
The Czech Republic became a member of the European Union in 2004, signed the Lisbon Treaty in 2007 and ratified it in 2009 as the last EU member.