Karl was a member of the Finnish-Swedish noble family
Horn af Kanckas. He was a son of the Swedish statesman
Henrik Klasson Horn (1512–1595) and Elin Arvidsdotter, née Stålarm (d. 1577). Carl married Agneta von Dellwig (d. 1611) in
Reval (Tallinn) in 1577. The marriage produced five daughters and six sons, including: • (1578–1618), Swedish diplomat and
Marshal of the Realm • (1583–1632), Governor-General of
Swedish Pomerania •
Evert (1585–1615), Swedish Field Marshal •
Gustav, Count of Björneborg (1592–1657), Swedish Field Marshal. Horn was born in Finland and later became a field commander and
Lagman in his homeland. He played an important role in the
Livonian War, distinguishing himself in the
Defense of Reval in 1570 and the subsequent
Battle of Ubagall in March 1571. He was also in command, together with his father
Henrik Klasson Horn, during the
Defense of Reval in 1577. He was sub-commander of
Pontus De la Gardie in the campaigns against Narva in 1579 and
1581. Horn was Swedish governor of Reval and
Swedish governor of Estonia from January 1576 to May 1578, and again from 1600 until his death. In between, on 19 February 1590 he was attacked at Narva by the Russians in the
Russo-Swedish War (1590–1595) and was compelled to sign an armistice, which obliged Sweden to surrender the territories won by the
Treaty of Plussa. For this, he was proclaimed a traitor by King
John III of Sweden, and imprisoned at
Örbyhus Castle until the death of King John III in 1592. After his release, he supported the Protestant
Duke Charles against the Catholic King
Sigismund III Vasa in the
War against Sigismund (1598–1599). He was mortally wounded at the beginning of the
campaign against Poland and died in the
Burtnieki Castle. His tomb is preserved in
St. Mary's Cathedral, Tallinn. ==References==