Flag of Denmark (Dannebrog) is the oldest state flag still in use. Flag has a white Scandinavian cross that extends to the edges of the flag on red field. As a representation of Christianity it inspired flags of many Nordic countries as Norway, Finland, Iceland, Aland Islands and the Faroe Islands. It also served as an inspiration for flags of the Scottish archipelagos of Shetland and Orkney.
Legend says that Dannebrog was given to the Danes by the God himself. On June 15, 1219, Danes fought a battle against Estonians near near Lyndanisse (Tallinn) in Estonia, battle also known as the Battle of Valdemar after the king that led it. While losing, Danish priest kneeled on the nearby hill and prayed to the God for the victory of the Danes. While he prayed the Danes were winning. A he was growing tired and his hands started to drop so the Danes started to lose. Two soldiers needed to hold his hands so he could continue to pray. Just before victory for the Danes, Dannebrog fell from the sky, King took it, showed it to the soldiers and they won the battle filled with courage that flag gave them. There is no historical record to support this legend. First text that mentions the legend is from 300 years after that battle and it connects flag with much smaller battle from 1208, still in Estonia, the battle of Fellin. There is also no evidence that this legend is true either.
Many historians have their theories of how and when flag appeared for the first time but they are all different. Caspar Paludan-Muller has a theory that Pope sent a flag to the Danish King so he can use it in his crusades in the Baltic countries. Johan Stockel thinks that flag was not sent to Danish king but to the Churchly legate in the North, Archbishop Andreas Suneson, again to be used in crusades in the Baltic countries but without Kings knowledge and to be used instead of the King’s symbol and with that to strengthen the power of the church. Adolf Ditlev Jorgensen has a theory that the flag is of the Knights Hospitaller. Fabricius and Helga Bruhn are telling that flag didn’t appear in the sky in the crucial moment of the battle bat that it was a cross of light. Similar stories appear in many places of Europe.
There are no historic documents of national flag in Danish literature of 12th and 13th century but there are several coins, seals and images that represent flags similar to Dannebrog. Earliest proof of how the flag of Denmark looked is in the Dutch armorial, the "Gelre Armorial" that is written between 1340 and 1370. In this book, on the page 55 is a draw in in color of a Danish coat-of-arms surmounted by a helmet near which is lance on which is hoisted a flag with a white cross on a red background. Text on the side of the drawing says “The King of Denmark”.