Hungary–Slovakia border
Drawn at Trianon in 1920 along the Danube and across the foothills of the Carpathians, leaving a large Hungarian population on the Slovak side. On the Danube a Cold War dam project turned into a case at the World Court.
Written from cited sourcesLast checked 29 September 2026Suggest a correction
See it on the globe:Hungary →Slovakia →
Trianon
Before World War I the whole area was part of the Kingdom of Hungary. At the peace talks, Czechoslovakia argued it needed the Danube as its border to be defensible, since nearly all rail links between Bohemia-Moravia and Slovakia ran through areas where Hungarians lived. Hungary asked for the 8,800 km² inhabited by 750,000 Magyars, but the Czechoslovak case won.[1]
The Treaty of Trianon of 4 June 1920 left Hungary with 32.9% of its prewar area and gave 21.8% of the lost land to Czechoslovakia. Along southern Slovakia the Hungarians formed a continuous population on both sides of the new frontier. A commission marked the line with a dense network of pillars between 1921 and 1925.[1]
Moved and moved back
The Vienna Award of 2 November 1938, which followed the Munich Agreement, returned the Magyar-inhabited south of Czechoslovakia to Hungary, and in 1939 Hungary occupied more of Slovakia.[1]
The peace treaty of 10 February 1947 declared the Vienna Award null and void and restored the 1938 border, with one change near Bratislava: land across the Danube from the city went to Czechoslovakia, and the Austrian tripoint moved to just northwest of the village of Rajka, whose dam and spillway stayed Hungarian.[1] In 1966 the US Geographer knew of no disputes over the line.[1]
The dams case
In 1977 Hungary and Czechoslovakia signed a treaty to build dams on the Danube in both countries, the Gabčíkovo–Nagymaros project, for power, flood control and navigation. In 1989 Hungary suspended and then abandoned its part, citing risks to its environment and to Budapest’s water. Czechoslovakia built an alternative, “Variant C”, on its own territory and put it into operation in October 1992, which changed Hungary’s access to Danube water.[2]
On 25 September 1997 the International Court of Justice found both sides in breach. Hungary had no right to abandon the works, and Czechoslovakia had no right to put Variant C into operation on its own. The 1977 treaty was still in force, with Slovakia as Czechoslovakia’s successor, and the court told the two countries to negotiate in good faith and settle the water released into the old Danube bed.[2]
Timeline
19204 June 1920
Treaty of Trianon
The Czechoslovak–Hungarian line is drawn along the Danube.[1]
1921–25
Demarcation
A commission marks the border with pillars.[1]
19382 November 1938
Vienna Award
Southern Slovakia returns to Hungary.[1]
194710 February 1947
Paris peace treaty
The 1938 line is restored, with a change near Bratislava.[1]
1977
Dams treaty
Hungary and Czechoslovakia agree to dam the Danube.[2]
1989
Hungary pulls out
Hungary suspends its part of the works.[2]
199725 September 1997
ICJ judgment
Both countries are found in breach.[2]
More borders
Sources
- [1]International Boundary Study No. 66: Czechoslovakia – Hungary Boundary · US Department of State, Office of the Geographer · 1 March 1966
- [2]Case concerning Gabčíkovo-Nagymaros Project (Hungary/Slovakia): Judgment (Press Communiqué 97/10) · International Court of Justice · 25 September 1997
Map geometry from Natural Earth via world-atlas. See credits.