German President Frank-Walter Steinmeier and Danish Queen Margarette II led celebrations Sunday marking 101 years since the two nations delineated their 70-kilometer (44 mile)-long border.

In June 1920, Danish King Christian X, Margerette's grandfather, ratified a law that returned the South Jutland region to Denmark.

North Schleswig was officially made part of Denmark and South Schleswig part of Germany as a result of the Schleswig plebiscites, a vote organized after World War One to determine the Danish-German border. 

At the time, residents of North Schleswig voted for the region to be made part of Denmark, and residents of South Schleswig voted for Germany, which retained the city of Flensburg and the North Sea island of Sylt. 

On Sunday, Germany's Schleswig-Holstein state premier Daniel Günther said at the ceremony that the border agreement represented an "unparalleled" instance of friendship.

"Where has it happened that a border was drawn peacefully by referendum?" Günther said at the centennial celebration, which had been postponed for a year by coronavirus. 

"In my eyes, it is of special historical merit that the border dispute of 1920 was not resolved by warlike confrontation, but by a referendum," Günther told Germany's DPA news agency. 

Germany was 'not always a good neighbor' to Denmark

During a speech at the ceremony, German President Steinmeier, decried Nazi Germany's 1940-1945 occupation of neutral Denmark, saying that the "peace promise" was violated 20 years after the border agreement when "we as Germans attacked our Danish neighbors.''

Steinmeier added that renewal of post-war border ties "was nothing less than a small miracle."

"Germany was truly not always a good neighbor to Denmark," said Steinmeier.

Together with Denmark's Queen Margarette, 81, Steinmeier planted ceremonial trees at the Dybbol fortress site near the Danish town of Sonderborg. 

Germany controlled the South Jutland region for 56 years after Denmark's 1864 defeat by Prussian troops at the Battle of Dybbol during the Second Schleswig War, sometimes described as Europe's forgotten war. The region was then called North Schleswig in Germany.

Battle casualties on the day included some 700 Danes and 263 German soldiers killed — losses still commemorated on April 18 each year by Denmark. 

Visiting the Dybbol fortress site with Steinmeier Sunday, Queen Margarethe said the historical site was now "a link between neighbors and friends."

Earlier on Sunday, Margarette as well as Denmark's Crown Prince Frederik and Prince Christian rode a horse-drawn carriage across the former German border at Frederikshoj, near Kolding.

Now deep within Denmark, it lies 70 kilometers (43 miles) north of the current German border city of Flensburg.

ipj/wmr (dpa, AP, AFP)