In 1918, Czechoslovak troops began occupying northern Hungary in accordance with the territorial promises that the Triple Entente made to Czechoslovak politicians during World War I. However, Slovakia (Upper Hungary) was occupied by Hungarian troops from the Hungarian Soviet Republic, who set up the Slovak Soviet Republic as a puppet regime. Its emblem was the red star, a symbol of communism. Following a brief war between Hungary, Czechoslovakia and Romania, Slovakia was incorporated into Czechoslovakia.