Slovakia
The Slovak Republic and the Czech Republic went their separate ways after 1 January 1993, an event sometimes called the Velvet Divorce. Slovakia has remained a close partner with the Czech Republic. Both countries co-operate with Hungary and Poland in the Visegrád Group. Slovakia became a member of NATO on 29 March 2004 and of the European Union on 1 May 2004. On 1 January 2009, Slovakia adopted the Euro as its national currency.
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.