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.
Slovak Republic (1939–1945)
After the Munich Agreement, Slovakia gained autonomy inside Czecho-Slovakia (as the former Czechoslovakia had been renamed) and lost its southern territories to Hungary under the First Vienna Award. As the Nazi Führer Adolf Hitler was preparing a mobilisation into Czech territory and creation of his Protectorate of Bohemia and Moravia, he had various plans for Slovakia. German officials were initially misinformed by the Hungarians that the Slovaks wanted to join Hungary. Germany decided to make Slovakia a separate puppet state under the influence of Germany, and a potential strategic base for German attacks on Poland and other regions.
On 13 March 1939, Hitler invited Monsignor Jozef Tiso, (the Slovak ex-prime minister who had been deposed by Czechoslovak troops several days earlier), to Berlin and urged him to proclaim Slovakia's independence. Hitler added that, if Tiso did not consent, he would have no interest in Slovakia's fate and would leave it to the territorial claims of Hungary and Poland. During the meeting, Joachim von Ribbentrop passed on a report claiming that Hungarian troops were approaching the Slovak borders. Tiso refused to make such a decision himself, after which he was allowed by Hitler to organise a meeting of the Slovak parliament ("Diet of the Slovak Land") which would approve Slovakia's independence.