Arad

A district of pre-World War I Hungary, occupied by France in 1919, at which time overprinted Hungarian stamps were issued. The district is now a part of Romania.

 

Banat, Backa

In 1918, Banat Republic was proclaimed in Temesvar, and government of Hungary has recognized its independence, but it was short-lived. After several days, Serbian troops entered Banat, and that was the end of the Banat Republic. In 1918 (confirmed by the Treaty of Trianon in 1920), most of the Banat became part of Romania. The southwestern part became part of the newly formed Kingdom of Serbs, Croats and Slovenes. A small area near Szeged became part of newly independent Hungary. The traditional heraldic symbol of the Banat is a lion, which is nowadays present in both, the Coat of Arms of Romania and the Coat of Arms of Vojvodina.
The territory of Backa united with the Kingdom of Serbia in 1918. By the Treaty of Trianon, the original territory of Backa was divided between Hungary and Kingdom of Serbs, Croats and Slovenes.

In 1919, postal authorities at Temesvar overprinted Hungarian stamps, which were used largely to pay the salaries of postal workers:

 

Baranya

Baranya county arose as one of the first comitatus of the Kingdom of Hungary, in the 11th century.
In 1918 (confirmed by the Treaty of Trianon in 1920), the south-east of the county became part of the newly formed Kingdom of Serbs, Croats and Slovenes. The remainder stayed in Hungary, as the present Hungarian county Baranya.
Serbian forces overprinted Hungarian stamps for use in the occupied territory in 1919:

 

Debrecen

A Hungarian district occupied by Romania after World War I, but later returned to Hungary.

 

Szeged

A city in southern Hungary. Between May and November 1919, Szeged was the seat of the anti-Bolshevik Hungarian National Government, under Admiral Horthy. In June 1919, the Horthy government overprinted 49 Hungarian issues for use in the area under its authority with overprint ‘Magyar Nemzeti Kormány Szeged' (Hungarian People's Government Szeged):

The occupying French forces prevented Horthy from attacking the Bolsheviks, but after the fall of the regime, the Nationalists occupied Budapest and established the National Republic.

 

Temesvar

A district of the Banat, occupied by Serbia after World War I. After the Serbian evacuation, Romanian forces occupied the area, and Temesvar was subsequently annexed by Serbia. Both Serbian and Romanian forces overprinted a total of 15 Hungarian stamps for use in the area.

Serbian occupation:

 

Romanian overprints:

 

Transylvania

Transylvania was occupied by Romanian forces after World War I. Governing bodies created by the Romanians of Transylvania, Bessarabia and Bukovina chose union with Romania, resulting in Greater Romania.