Czech Republic–Slovakia relations
Before 1918, both countries were part of Austria–Hungary. However, after the Ausgleich of 1867 Czechia belonged to the Austrian Empire while Slovakia belonged to the administratively separate Kingdom of Hungary, and between 1918 and December 31, 1992, both countries were part of Czechoslovakia. 
Both countries established diplomatic relations on January 1, 1993. These international relations are usually referred to or described as "very good", "cordial", and "above standard" in the media. When a Czech or Slovak president is inaugurated, very often his first international visit is to the former part of the common country. The same custom applies to newly elected prime ministers of the Czech Republic and Slovakia.
Czech Republic
Czechoslovakia remained the only democracy in this part of Europe in the interwar period. However, the Czech part of Czechoslovakia was occupied by Germany in World War II, while the Slovak region became the Slovak Republic; Czechoslovakia was liberated in 1945 by the armies of the Soviet Union and the United States. Most of the three millions of the German-speaking minority were expelled following the war. The Communist Party of Czechoslovakia won the 1946 elections and after the 1948 coup d'état, Czechoslovakia became a one-party communist state under Soviet influence. In 1968, increasing dissatisfaction with the regime culminated in a reform movement known as the Prague Spring, which ended in a Soviet-led invasion. Czechoslovakia remained occupied until the 1989 Velvet Revolution, when the communist regime collapsed and market economy was reintroduced. On 1 January 1993, Czechoslovakia peacefully dissolved, with its constituent states becoming the independent states of the Czech Republic and Slovakia. The Czech Republic joined NATO in 1999 and the EU in 2004.