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.
Second Czechoslovak Republic
In January 1939, negotiations between Germany and Poland broke down. Hitler scheduled an invasion of Bohemia and Moravia for the morning of 15 March. In the interim, he negotiated with the Slovak People's Party and with the Kingdom of Hungary and its representatives for the Hungarian minority in Slovakia to prepare the dismemberment of the Second Czechoslovak Republic before the invasion. On 13 March he invited Monsignore Jozef Tiso to Berlin, where he offered Tiso the option of proclaiming the Slovak state and seceding from Czecho-Slovakia. In such a case, Germany would be Slovakia's protector and would not allow the Hungarians to press on Slovakia any additional territorial demands. If the Slovaks declined, Germany would occupy Bohemia and Moravia and disinterest himself in Slovakia's fate—in effect, leaving the Slovaks to the mercies of the Hungarians and the Poles (Poland had claimed the Slovak Spiš territory since the Polish-Czechoslovak War). During the meeting, Joachim von Ribbentrop passed on a (false) report saying that Hungarian troops were approaching Slovak borders. Tiso refused to make such a decision himself, after which he was allowed by Hitler to organize a meeting of the Slovak parliament ("Diet of the Slovak Land"), which would approve Slovakia's independence.