, after which the house of Holstein-Gottorp is named of the Duchy of Holstein-Gottorp (from
Siebmachers Wappenbuch) In 1544, the so-called "one-third duchy" was ceded to
Adolf, third son of King
Frederick I of Denmark and the youngest half-brother of King
Christian III of Denmark. Thus, the surviving House of Holstein-Gottorp is a cadet branch of the
House of Oldenburg. The Dukes of Holstein-Gottorp shared the uneasy rule of Schleswig and Holstein with the Kings of Denmark. As such, they were often allies (practically clients) of the Swedes, enemies of the Danes. This longtime alliance was sealed by several dynastic marriages:
Christina of Holstein-Gottorp married
Charles IX of Sweden,
Hedwig Eleonora of Holstein-Gottorp married
Charles X Gustavus,
Duke Frederick IV married the eldest daughter of King
Charles XI of Sweden, and ultimately Prince
Adolf Frederick of Holstein-Gottorp ascended to the Swedish throne in 1751, founding the Holstein-Gottorp dynasty of Sweden (ruled 1751–1818). By the
Treaty of Roskilde (1658) and the
Treaty of Copenhagen (1660),
Denmark-Norway released Gottorp from its feudal bonds and recognized the sovereignty of its dukes over the Gottorp portions of the duchy of Schleswig. In fact, these Schleswigers had been relatively independent already for more than a century. Although the duchy of Holstein remained officially a fief of the Empire, in fact by treaty its dukes co-governed both duchies with their formal overlord, the Danish king.
Gottorp question In the
Great Northern War, the duchy sided with
Sweden and was defeated after Danish troops occupied the northern portions of Holstein-Gottorp. According to the 1720
Treaty of Frederiksborg, Swedish support for Gottorp ceased, making it impossible for the dukes to regain their lost territories in Schleswig and prolonging their feud with the king of Denmark. Following the peace settlement of 1721,
Duke Charles Frederick fled to the court of
Peter the Great of
Russia, and for some time, the Russians plotted to restore Charles Frederick to his lands in Schleswig. Charles Frederick himself was married to
Grand Duchess Anna, Peter's daughter. Peter II and his successors abandoned the policy of Peter the Great of backing the claims of the dukes of Holstein-Gottorp on their part of Schleswig. In fact, to gain a port on the coast of the Northern sea, Russia needed not Schleswig but the friendship of dukes. But from this marriage was born
Charles Peter Ulrich, who succeeded to Holstein-Gottorp in 1739, and became an heir to the Russian throne according to the will of
Catherine I and especially upon the accession of his childless aunt
Elizabeth in 1741. Charles Peter Ulrich, who acceded to the Russian throne as Peter III in 1762, was determined to reclaim his part of Schleswig from
Denmark–Norway and to attach it to Holstein. When he became emperor in 1762, he immediately signed a generous peace with
Prussia and withdrew
Russia from the
Seven Years' War in order to concentrate fully on an attack upon Denmark together with Prussia. This move was unpopular in Russia, since it was considered a betrayal of Russia's sacrifices in the war, as well as placing national interests in jeopardy. At the same time, the Danish army had hastily moved across the border into
Mecklenburg, to deter an invasion of Holstein, and prepared for battle. The Russian army had advanced to less than 30 km from the Danes when it learned that Peter III had been overthrown by his wife, who acceded to the throne as Empress
Catherine II. One of her first actions was to call off the war against Denmark, surrender territorial claims, and restore normal relations. Peter III's son,
Paul, the new Duke of Holstein-Gottorp, was a minor under the regency of his mother, the empress. With the 1773
Treaty of Tsarskoye Selo, she agreed to cede the territorial claims of her son to the Holstein-Gottorp lands still held by Denmark and to cede the part of Duchy, held by her husband, obtaining in exchange the German countships of
Oldenburg and
Delmenhorst, elevated in 1776 into the duchy of Oldenburg within the Holy Roman Empire. The duchy was given to the cousin of Paul's grandfatherthe aged
Prince-Bishop of Lübeck,
Frederick August, head of a younger branch of the Holstein-Gottorp family. This put an end to the
Gottorp question, which had generated so many conflicts between the Nordic powers. The House of Holstein-Gottorp acceded to several European thrones. The dynastic policy of the dukes of Holstein-Gottorp resulted in its cadet branch, the Swedish line, ruling
Sweden from 1751 until 1818 and
Norway from 1814 to 1818. In 1863, the related
House of Schleswig-Holstein-Sonderburg-Glücksburg — descended from King Christian III of Denmark — became
Kings of Denmark and
Greece and, in 1905, of
Norway. The Lübeck branch became first
dukes and later grand dukes of Oldenburg from (1773 until 1918), while the
senior branch ruled
Russia briefly in 1762 and then again from 1796 until 1917 (while in 1762–1796 it was ruled by their
widow, second cousin and mother). However although agnatic members of this house reigned in Russia, they were commonly called Romanov, or more rarely, Holstein-Gottorp-Romanov. ==Dukes of Schleswig-Holstein-Gottorp==