In 1219, Valdemar gathered his fleet, joined forces with the Rugian navy led by prince Wizlav of Rügen, and landed on the northern coast of Estonia in the Lindanise (now Tallinn) harbor in the Estonian province of Revala. According to the legend, the national flag of Denmark "Dannebrog" was born at this time, falling from the sky during a critical moment in the fight and helping the Danes to win the Battle of Lindanise against the Estonians. The date of the battle, June 15, is still celebrated as "Valdemarsdag" (the national "flag day") in present-day Denmark.