Page "Danish Estonia" Paragraph 5

In 1219, Valdemar gathered his fleet, joined forces with the Rugian navy led by prince Wizlav of Rügen and landed at Northern Coast of Estonia in the Lyndanisse ( now Tallinn ) harbor in an Estonian province of Revala.

According to the legend, the national flag of Denmark Dannebrog was born at the time by falling from the sky during a critical moment in the fight and helped the Danes to win the Battle of Lyndanisse against the Estonians.

The date of the battle, June 15, is still celebrated as Valdemarsdag ( the national " flag day ") in present day Denmark.