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.
Collaboration with the Axis Powers
The Slovak Republic ("Slovenská republika") was a quasi-independent ethnic-Slovak state which existed from 14 March 1939 to 8 May 1945 as an ally and client state of Nazi Germany. The Slovak Republic existed on roughly the same territory as present-day Slovakia (with the exception of the southern and eastern parts of present-day Slovakia). The Republic bordered Germany, the Protectorate of Bohemia and Moravia, the German-occupied Poland, and Hungary.