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
Despite the mobilization of 1.2 million-strong Czechoslovak army and the Franco-Czech military alliance, 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.