The Livonian Crusade took place during a period of Danish expansion and consolidation in the Baltic region, a key focus for Denmark under King Valdemar II. By the late 12th and early 13th centuries, Denmark was asserting itself as a major power in northern Europe, actively seeking new territories across the Baltic Sea. This expansion was intertwined with the broader Christianization efforts of the Northern Crusades, sanctioned by the Papacy to convert the last pagan regions of Europe, including Livonia (modern Latvia) and Estonia.
Denmark’s involvement in the Livonian Crusade must be seen against the backdrop of its ambitions in the Baltic. While German crusaders, led by the bishops of Riga, had initiated the conquest of Livonia and parts of Estonia, Denmark turned its eyes to the northernmost reaches of the region, particularly Estonia, where Valdemar II saw an opportunity for Danish influence.
In 1219, responding to an appeal for help from the Bishop of Riga, Valdemar launched his invasion of Estonia. The Danes achieved a decisive victory at the Battle of Lindanise, near present-day Tallinn. According to Danish legend, it was during this battle that the Dannebrog, the Danish national flag, miraculously fell from the sky, ensuring the Danish victory. This victory allowed Denmark to establish control over northern Estonia, where they built the fortress of Tallinn (then known as Castrum Danorum, or "Castle of the Danes"). This marked the creation of the Danish Duchy of Estonia, formally recognized as part of Valdemar’s realm.
Despite Danish success, the region was unstable. The Estonian tribes fiercely resisted Christianization and foreign rule, launching several uprisings. During the major Estonian rebellion of 1223, nearly all Christian strongholds in Estonia, except for Tallinn, were overrun, and the local populations reverted to pagan practices. However, with the help of the crusaders, Denmark managed to reconsolidate its control over northern Estonia by 1227.
Denmark's expansion into the Baltic brought it into direct competition with other powers, including the German crusading orders and the Republic of Novgorod. While Denmark’s focus remained on Estonia, it maintained complex relations with the Livonian Brothers of the Sword, the German military order leading the crusades further south. After the catastrophic defeat of the Brothers of the Sword at the Battle of Saule in 1236, the surviving knights merged with the Teutonic Order, which then became Denmark’s primary rival in the region.
The Treaty of Stensby in 1238 restored Danish control over the Duchy of Estonia, which had briefly fallen into the hands of the Teutonic Knights. However, this arrangement was unstable, and Danish power in the region eventually waned. Following the St. George's Night Uprising in 1343, where Estonians once again revolted against foreign rule, Denmark decided to sell its Estonian territories to the Teutonic Order in 1346, ending its direct involvement in the Baltic crusades.
Throughout this period, Denmark’s involvement in the Livonian Crusade reflected its broader ambitions to dominate the Baltic Sea and secure its position as a regional power. Though initially successful in gaining control over northern Estonia, Denmark's hold proved fragile, and by the mid-14th century, it had ceded its Baltic territories to the powerful Teutonic Order, which would go on to dominate much of the region until the 16th century.