The International Commission controlled the two zones until 15 June 1920.
As from 5 May, Zone 1 was gradually transferred to Danish sovereignty and Zone 2 was correspondingly returned to German rule.
In Denmark, the Reunification was marked by a week of celebrations.
King Christian X signed the assimilation of the Southern Jutland regions into law at a meeting of the Sovereign Council on 9 July and then participated in a popular celebration in the Danish capital, Copenhagen.
In the evening, the Danish royal family and government sailed to Southern Jutland, and on the following day the Danish king rode across the now-defunct 1864 border.
This marked the start of the official reunification party at Dybbøl Fortifications on 11 July, which was attended by the Danish royal family, the Danish government and around 50,000 other guests.
Over the next four days, the Danish royal family toured various parts of Southern Jutland, to the acclaim of the local residents.
The biggest celebration in Germany was held on 17 June, when the German troops who had been expelled during the run-up to the referendum returned to Flensburg and received a heroes’ welcome from the town’s citizens, the mayor and the German Minister of Foreign Affairs.