His subsequent accessions to the thrones of Norway (in 1450) and Sweden (in 1457) restored the unity of the Kalmar Union for a short period.

In 1464, Sweden broke away from the union and Christian's attempt at a reconquest resulted in his defeat by the Swedish regent Sten Sture the Elder at the Battle of Brunkeberg in 1471.

[citation needed] Through his father, he belonged to the House of Oldenburg, a comital family established since the 12th century in an area west of the River Weser in north-western Germany.

Based on the two strongholds of Oldenburg and Delmenhorst, the family had gradually expanded its rule over the neighbouring Frisian tribes of the area.

Christian's mother, Hedvig, was a daughter of Gerhard VI, Count of Holstein, and a sister of Adolphus, Duke of Schleswig.

His death resulted in the break-up of the union of the three kingdoms, as Denmark and Sweden went their separate ways and Norway's affiliation was unclear.

The council also demanded that Christian should marry dowager queen Dorothea of Brandenburg (ca 1430–1495), widow of his predecessor King Christopher III.

His coronation was held on 28 October 1449, in the Church of Our Lady in Copenhagen, at which occasion his marriage with dowager queen Dorothea was also celebrated.

In February 1449, a part of the Council declared in favour of Karl as king, but on 15 June the same year, a different group of councillors paid homage to Christian.

He received the power from temporary Swedish regents Archbishop Jöns Bengtsson Oxenstierna and lord Erik Axelsson Tott.

[5][6][7][8] In 1460 King Christian also became Duke of Schleswig, a Danish fief, and Count of Holstein-Rendsburg, a Saxe-Lauenburgian subfief within the Holy Roman Empire.

[citation needed] In 1474 Christian travelled two times: in April he went to Milan (his stay in Lombardy is celebrated by frescoes by Il Romanino in the Malpaga Castle) and Rome, in Italy, where he met Pope Sixtus IV.

The burials of Christian I and Queen Dorothea are marked with a pair of simple stones, as the chapel itself was to be considered their sepulchral monument.