Have you noticed all the Danish flags waving everywhere in the cityscape in Denmark right now? Right now, most of them are due to Denmark's participation in the European Championship in football, and here they are an expression of joy and support for our national football team.
However, many foreigners wonder about the Danes' enthusiasm for the flag. But in Denmark, “Dannebrog”, i.e., the name of the flag, is not only a symbol of the country Denmark. It is also a national symbol, of course - Dannebrog is the flag of Denmark - but we also use the flag to celebrate everything from birthdays and the new students to, of course, the European Championships and the World Cup in football, just as flags are used as decorations on birthday cakes and on the Christmas tree. Which is quite another story, by the way - Danes can discuss for hours whether the flag garlands should hang down horizontally or vertically on the Christmas tree. Personally, I don’t use flags on my Christmas tree and thus avoid quarrels…
Now one might well think that the Danes are very nationalistic in our widespread use of the flag - and parts of the political right wing actually use Dannebrog in their politics when they address the "Danes" - and not just the citizens. So the question is: How can Danes be nationalistic on the one side (and some Danes are) and use the flag merely as decoration on the other? Probably, the truth is that most Danes simply associate Dannebrog with party and joy and not with politics.
The myth is that Dannebrog fell from the sky during a battle outside Tallinn in Estonia on June 15, 1219. Valdemar Sejr (“Sejr” means “victory”) won the battle and thus the dominion over northern Estonia. That's why you always flag on Valdemar's day on 15 June. In Vordingborg, where I come from, it is an important day because Valdemar's castle with the Goose Tower was here.
From the Middle Ages until approx. 1800, Dannebrog was primarily a symbol of the king's power and not a symbol of the nation of Denmark. It only really became a symbol of Denmark, Danes and “Danishness” after the war in 1864, when Denmark lost the 2nd Schleswig war to Germany, and where Southern Jutland was German until the reunification in 1920.