Danish territorial expansion reached its height under Valdemar II (1202-1241) who forced the king of Norway to pay him homage, gained recognition of Danish rule in northern Germany by Frederick II in return for his support against Otto IV and conquered Estonia in 1219. However, defeat in the Battle of Bornhoved in 1227 and collapse of Danish overlordship in northern Germany marked the end of Denmark as great power. The Kingdom of Denmark retained only Rugen and Estonia.
Eric V “Klipping”
Three Valdemar’s sons succeeded him in turn: Eric IV (1241-1250), Abel (1250-1252) and Christopher I (1252-1259). The reign of Eric V “Klipping” (1259-1286) was marked by struggles between the king and powerful nobles which resulted in the issue of handfastening in 1282 which greatly limited the royal power, like the English Magna Carta. His successor Eric VI Menved launched a large-scale expansionist policy in northern Germany which almost caused bankrupt and provoked a dangerous rebellion in Jutland in 1313 that had to be suppressed with German military assistance. The central authority continued to decline and Eric’s successor Christopher II (1320-1326) was deposed when he tried to improve the financial state by raising taxes of nobles and clergy.
Struggle for the Danish throne that followed the deposition of Christopher II in 1326 was won by Gerhard III of Holstein who was appointed regent and guardian of his protegee Valdemar III (1326-1329). Gerhard III of Holstein was de facto ruler of Denmark but he became very unpopular and was killed in 1340. The Danish throne was assumed by Valdemar IV (1340-1375) who restored the royal authority, extended the Danish territory to its former extent and was triumphal over the powerful Hanseatic League but only for a short period. He was forced to sign the Treaty of Stralsund in 1370 which ensured the Hanseatic League a trade monopole in Scandinavia and Baltic coast.
Valdemar IV died without a male descendant. His daughter Margaret I, Queen of Norway achieved election of her son Olav IV Haakonsson as Oluf II of Denmark (1376-1387). Margaret’s son also succeeded his father Haakon IV as Olav IV of Norway and united Norway and Denmark in a personal union. Olav IV died without an heir to the throne in 1387 and was succeeded by his mother Margaret I as Queen of Denmark and Norway. She defeated and captured the Swedish king, Albert of Mecklenburg in 1389 and added to her title Queen of Sweden. Margaret I assured the throne of Denmark, Norway and Sweden to her great-grandson Eric of Pomerania on the congress of the three Councils of the Realm at Kalmar which united the three kingdoms into the Kalmar Union under Eric of Pomerania. However, Margaret I wasde facto ruler of all three kingdoms until her death.
Eric of Pomerania or Eric VII (1412-1439) did not follow Margaret’s skillful policy of diplomacy and started a war against Holstein over South Jutland (Schleswig). Eric’s attempts to drive out the German merchants from the Baltic coast resulted in conflict with the cities of the Hanseatic League which joined Holstein against Eric. Eric VII failed to conquer South Jutland and lost the lands he had already gained. Heavy taxes and centralization of government caused an unrest which led to national and social rebellion known as the Engelbrekt rebellion in Sweden in 1434. The rebellion that was joined by the nobles resulted in the expulsion of the Danish forces from Sweden. Meanwhile arose opposition against Eric VII in Denmark leading to his deposition in 1439.
The Danish Council of the realm elected Christopher of Bavaria (1439-1448) who was also elected in Norway and Sweden. Christopher pursued Margaret’s policy of diplomacy and ruled each country through its council of the realm and its own laws. Christopher died without an heir to the throne in 1448. Christian I of Oldenburg (1448-1481) was elected in Denmark and Norway, while Sweden elected Charles Knutsson. However, his attempt to restrict the power of nobility resulted in bitter opposition and he was forced to leave Sweden. Swedish Council of the realm elected Christian I as his successor in 1457, while Denmark and Norway meanwhile signed the Treaty of Bergen which strengthened the union between both realms. Christian I was also elected Count of Holstein (in 1474 Holstein was elevated to a Duchy) when he inherited the Duchy of Schleswig to prevent an eventual division of Schleswig-Holstein. He was succeeded by John (1481-1513) whose reign was marked by the first Danish-Russian alliance against Sweden.