Knowledge of Danish antiquity is derived largely from archaeological research. Some historians believe that Danes inhabiting the southern part of the Scandinavian Peninsula migrated to the Jutland Peninsula and the adjacent islands in the Baltic Sea in the 5th and 6th centuries. Evidence of major public structures—including a canal, a long bridge, and the ramparts across the neck of Jutland now called the Danevirke—in the 8th century attests to the presence of a fairly strong central authority in Jutland on the eve of the Viking age.

Within a century of their first raid on the British Isles in the 780s, the Danes were masters of the part of England that became known as the Danelaw. Under King Harold Bluetooth in the 10th century, political consolidation increased, and the Christianization of the Danes was begun. Harold’s son, Sweyn I, conquered all of England in 1013 and 1014. Sweyn’s son, Canute II, who ruled England (1016-1035) and Denmark (1018-1035), completed the Christianization of Denmark.

Edward the Elder (died 924), king of Wessex (899-924), son of King Alfred. He succeeded as king of the Angles and Saxons in 899, despite a rebellion led by his cousin Ethelwald with the support of the Danes of Northumbria and East Anglia. After a protracted struggle he defeated the Danes, and in 912, on the death of his brother-in-law Ethelred, alderman of Mercia, he annexed the cities of London and Oxford and their environs. The Danes submitted formally in 918, and soon thereafter the sovereignty of Edward was acknowledged by the North Welsh, the Scots, the Northumbrians, and the Welsh of Strathclyde. Edward was succeeded by his son Athelstan.

Edmund I (921-46), Saxon king of the English (939-46), the son of King Edward the Elder. He participated in the Battle of Brunanburh in 937 and succeeded his half brother Athelstan as king in 939. The following year Olaf Godfreyson, a Viking ruler of Dublin, seized the territory of Northumbria in northern England and extended his rule as far south as Leicester. After Olaf's death in 941, Edmund made war on the Vikings, expelling them from the country three years later. In 945 Edmund occupied the kingdom of Strathclyde, west of Northumbria, and turned it over to his ally Malcolm I MacDonald, king of Scotland. The following year Edmund was stabbed to death by a robber and was succeeded by his brother Edred (reigned 945-55). Edmund was known as a legal reformer, especially for his restrictions on the blood feud.

Edgar, called The Peaceful (944-75), Saxon king of the English (959-75), younger son of King Edmund I. In 957, during the rule of his brother, King Edwy, Edgar was chosen by the Mercians and Northumbrians to be their sovereign. One of his first acts was to recall the monastic reformer St. Dunstan, whom Edwy had exiled; Edgar subsequently made Dunstan bishop of Worcester and London and archbishop of Canterbury. In 959 Edgar succeeded to the entire English Kingdom. His reign was notable for the establishment of national consolidation, reformation of the clergy, improvement of the judiciary system, and formation of a fleet to defend the coast against the Scandinavian Vikings.

Edward the Martyr (circa 963-78), Anglo-Saxon king of England, son of King Edgar. A boy at the time of his father's death, Edward ruled under the guidance of St. Dunstan, archbishop of Canterbury. His brief reign was marked by agitation against the monasteries, which Edgar had favored at the expense of the nonmonastic clergy. Edward was assassinated, possibly at the instigation of his stepmother Elfrida (Aelfthryth), whose son Ethelred succeeded him. Miracles were said to have occurred at his tomb, and he was later declared a saint and martyr. Edward's feast day is March 18.

Ethelred II, called The Unready (968?-1016), Anglo-Saxon king of England (978-1016), son of King Edgar and half brother of Edward the Martyr. His reign was marked by bitter military struggles. After negotiating a treaty with Richard II, duke of Normandy (reigned about 996-1026), Ethelred married Richard's sister Emma. This marriage provided the basis for the subsequent Norman claim to the English throne. Although Ethelred paid tribute to the plundering Danes, Sweyn I (the Forkbeard), king of Denmark, invaded England in 1013 and proclaimed himself king. In 1014 Ethelred fled to Normandy but returned a few months later upon Sweyn's death. Sweyn's son and successor, Canute II, invaded the country a year later and, following Ethelred's death, became king of England. Ethelred's sobriquet, "The Unready," is a corruption of the Old English unraed, "bad counsel," which is a reference to his misfortunes.

Canute, the son of Sweyn I Forkbeard, king of the Danes, conquered England in 1013. When his father died the following year, he was proclaimed king of England by his Danish warriors. However, the witenagemot, an advisory body to the Anglo-Saxon kings, reinstated King Ethelred, and Canute fled. He returned in 1015 and soon subjugated all of England, except London. After Ethelred's death in 1016, the Londoners named his son, Edmund II, king. During an ensuing struggle, the Londoners were defeated at Ashingdon, Essex, in October 1016. The following month Edmund died and Canute emerged the undisputed king. A wise and effective ruler, he reconciled with the English and maintained peace with the Continental powers. To that end he married King Ethelred's widow, Emma of Normandy, supported the church, and in 1027 went to Rome for the coronation of Holy Roman Emperor Conrad II. For administrative purposes he divided England into the four earldoms of Mercia, Northumberland, Wessex, and East Anglia.

Hardecanute (Danish Hardeknud) (circa 1019-42), king of Denmark (1035-42) and last Danish king of England (1040-42), probably born in Denmark. He was the son of King Canute and Emma of Normandy and thus the heir to the English realm. When Canute died, however, Hardecanute was in Denmark, and his illegitimate half brother, Harold Harefoot, who was then in England, took control of that country; he was accepted as King Harold I by the witenagemot (royal council) in 1037. The ensuing struggle between the two brothers was ended only by the death of Harold in 1040. Hardecanute, then officially chosen as king by the witenagemot, was unpopular with his subjects and left the control of the realm to his mother and the powerful Godwin, earl of Wessex. Hardecanute was succeeded in Denmark by Magnus I (the Good), king of Norway, and in England by his half brother Edward the Confessor.

Edward the Confessor (1002?-66), king of England (1042-66), son of King Ethelred the Unready. During most of the rule of the Danish kings of England who followed Canute II, Edward lived at the court of the dukes of Normandy. In 1041, Hardecanute invited Edward to England, and the following year Edward succeeded to the English throne, largely because of the support of Godwin, earl of Wessex. Edward married Godwin's daughter Edith but soon gave his favor to the enemies of Godwin, who was harassed and for a brief time exiled. Perhaps because of Godwin's popularity in England, a reconciliation was effected about 1052. Godwin's son Harold, later Harold II of England, became one of Edward's advisers, and another son, Tostig, became his favorite. In 1055, Edward made Tostig earl of Northumbria, but the earl's rule was so oppressive that a rebellion broke out in 1065, and Edward was forced to exile him. Thereafter, Edward's health failed, and he was unable to attend the consecration of Westminster Abbey, which he had founded. He was succeeded by Harold II, the last Saxon king of England. Less than a century after his death, Edward was canonized.

Olaf Sihtricson, known in sagas as Olaf the Red (died 981?), Danish king of Northumbria (940-44, 949-52) and king of Dublin (944-49, 952-80). In 940-41 Olaf ruled Northumbria jointly with his cousin Olaf Godfreyson. He was expelled from his English domain in 944. Thereupon he went to Ireland. He reigned in Dublin until 949, when he regained the Northumbrian throne. After his second expulsion from England in 952, he governed his Irish kingdom until his defeat by fellow Danes at Tara in 980. Soon afterward he died in exile at Iona in the Hebrides Islands.

Olaf I, full name OLAF TRYGGVASON (968-1000), king of Norway (995-1000). A great-grandson of King Harold I, he was brought up in Russia and later participated in numerous Viking raids along the Baltic and North Sea coasts and in the British Isles. During his last campaign, in England (994) with Sweyn I Forkbeard of Denmark, he was converted to Christianity, and the following year he returned to Norway, where a rebellion had erupted against the pagan Earl Håkon. The victorious Olaf founded the city of Nidaros (now Trondheim) as his capital and set out to Christianize the country. Only partly successful in Norway, his efforts contributed to the conversion of Iceland, Greenland, and the Faroe Islands to Christianity. Olaf's forces were defeated by a coalition consisting of Sweyn Forkbeard, King Olaf of Sweden, and the two sons of Earl Håkon in the naval Battle of Svold (1000), during which Olaf lost his life.

A temporary decline in Danish power after the death of Christopher II in 1332 was followed, in the reign of Waldemar IV, by the reestablishment of Denmark as the leading political power on the Baltic Sea. However, the Hanseatic League, a commercial federation of European cities, controlled trade.

In 1380 Denmark and Norway were joined in a union under one king, Olaf II, a grandson of Waldemar IV, and with Norway came Iceland and the Faroe Islands. After Olaf’s death in 1387, his mother, Margaret I, reigned in his stead. In 1389 she obtained the crown of Sweden and began the struggle, completed successfully in 1397, to form the Union of Kalmar, a political union of the three realms. Denmark was the dominant power, but Swedish aristocrats strove repeatedly—and with some success—for Sweden’s autonomy within the union. The Kalmar Union lasted until 1523, when Sweden won its independence in a revolt against the tyrannical Christian II led by Gustav Vasa, who was elected king of Sweden as Gustav I in that year.

Also in 1523 Christian II was driven from the Danish throne. There followed a period of unrest, as Lübeck, the strongest Hanseatic city, interfered in Danish politics. With help from Sweden’s king, Lübeck’s interference was ended and Christian III consolidated his power as king of Denmark. During his reign (1534-1559) the Reformation triumphed in Denmark, and the Lutheran church was established as the state church. At this time the Danish kings began to treat Norway as a province rather than as a separate kingdom. Commercial and political rivalry with Sweden for domination of the Baltic Sea resulted in the indecisive Nordic Seven Years’ War (1563-1570) and the War of Kalmar (1611-1613) between Sweden and Denmark.

The intervention of Christian IV in the religious struggle in Germany on behalf of the Protestant cause in the 1620s led to Danish participation in the Thirty Years’ War. Continued rivalry with Sweden for primacy in the north led to the Swedish Wars of 1643 to 1645 and 1657 to 1660, in which Denmark was badly defeated and lost several of its Baltic islands and all of its territory on the Scandinavian Peninsula except Norway.

Economic reverses resulting from these defeats had far-reaching consequences in Denmark. The growing commercial class, hard hit by the loss of foreign markets and trade, joined with the monarchy to curtail the power and privileges of the nobility. In 1660, capitalizing on the nobility’s unpopularity after its poor military performance in the Swedish Wars, Frederick III carried out a coup d’état against the aristocratic Council of the Realm. The monarchy, which until then had been largely dependent for its political power on the aristocracy, was made hereditary, and in 1661 it became absolute. The tax-exemption privileges of the nobility were ended, and nobles were replaced by commoners in the nation’s administrative apparatus. Important administrative reforms were also introduced.

A growing demand for constitutional government in Denmark led to the proclamation of the constitution of 1849. Denmark became a constitutional monarchy, civil liberties were guaranteed, and a bicameral legislature, which was to share legislative power with the Crown, was established. German nationalism in Schleswig and Holstein (see Schleswig-Holstein), both hereditary duchies held by the kings of Denmark, presented the Danes with serious problems in the wake of the Revolution of 1848. The two duchies had long been objects of dispute between Danish kings and German monarchs. With diplomatic aid from Russia, Denmark had prevailed in a first test of strength in mid-century, but in 1864 Prussia and Austria went to war with the Danes to prevent incorporation of Schleswig into Denmark’s territory and constitutional structure. The Danes were defeated and lost possession of the two duchies and of other territory.

The country was neutral during World War I (1914-1918). In 1917 Denmark sold the Virgin Islands, in the West Indies, to the United States. Constitutional reforms enacted in 1915 established many of the basic features of the present governmental system. Universal suffrage went into effect in 1918. The same year Denmark recognized the independence of Iceland, but continued to exercise pro forma control of the foreign policy of the new state, and the Danish king remained Iceland’s head of state. In 1920 North Schleswig was incorporated into Denmark as a result of a plebiscite carried out in accordance with the terms of the Treaty of Versailles; the southern part of Schleswig had voted to remain in Germany.

Four decades of dominance by the Social Democratic party ended with the 1968 elections. Hilmar Baunsgaard, leader of the Radical Liberal party, formed a coalition government that lasted until 1971, when Jens Otto Krag, a former Social Democratic prime minister, retained office. King Frederick IX died in 1972 and was succeeded by his daughter, Margaret II. Later that year Krag resigned and was replaced as prime minister and party leader by Anker Jørgensen. The Social Democrats suffered losses in the elections of late 1973, and Poul Hartling, a Liberal, formed a minority cabinet. Following elections in early 1975, however, Jørgensen returned to power, also at the head of a minority government. He retained his leadership until September 1982, when Poul Schlüter, a Conservative, was named to head a right-of-center coalition. Elections in January 1984 increased the plurality of the coalition, which retained power in the elections of September 1987, May 1988, and December 1990. In 1985 the Folketinget passed legislation against future construction of nuclear power plants in the country, and the government agreed to help establish a Nordic nuclear-free zone. Disputes in the Danish government over NATO-related policies damaged Denmark’s relationship with the organization, but good relations were largely restored by 1988. Destruction of lobster colonies in the strait between Denmark and Sweden in 1988 and other ecological disasters resulted in the passage of rigorous environmental protection measures by the Folketinget.

In the wake of a scandal concerning immigration visas, Prime Minister Schlüter resigned in January 1993. A new majority coalition government was formed, with Social Democrat Poul Nyrup Rasmussen as prime minister. In 1992 Danish voters narrowly rejected the Maastricht Treaty, which provided for increased political and monetary integration within the European Community (now the European Union). After modifications to the pact that promised exemptions from certain standards for Denmark, the Danes voted their approval in May 1993. In elections held in September 1994, the coalition headed by Rasmussen retained power, but lost its majority in the Folketinget.

Harold Bluetooth (died about 985), king of Denmark (circa 940-85), who consolidated the Danish realm as a unitary kingdom. He was the son of Gorm the Old (d. about 940) and inherited his kingdom, centered on Jelling in Jutland. Although he temporarily (974-83) lost southern Jutland to Holy Roman Emperor Otto II, Harold secured all Denmark under his control and extended his rule to much of Norway. Baptized in 960 and thus introducing Christianity into Denmark, he had the famous Jelling rune stone erected in his parents' memory. Harold was fatally wounded during a rebellion by his son and successor, Sweyn I.

Frederick I (of Denmark and Norway) (1471-1533), king of Denmark and Norway (1523-33), son of Christian I and brother of King Hans. He was elected to succeed his deposed nephew, Christian II. Owing his throne to the nobles, Frederick granted them many privileges, thereby diminishing the royal power. A sympathizer of Lutheranism, he facilitated the spread of that faith in his dominions.

Frederick II (of Denmark and Norway) (1534-88), king of Denmark and Norway (1559-88), son of Christian III. He began his reign by conquering the independent republic of Dithmarschen (now a region of Germany) in the western part of the duchy of Holstein. Encouraged by his success, he began a war with Sweden in 1563; it was, however, settled under the Peace of Stettin (1570) with little gain for Denmark. During the latter part of his reign, which was peaceful, he suppressed piracy on the North and Baltic seas and built the fortress-castle of Kronborg in Helsingør (Elsinore). The castle is the setting of Shakespeare's Hamlet.

Frederick III (of Denmark and Norway) (1609-70), king of Denmark and Norway (1648-70), born in Haderslev, Denmark, the second son of King Christian IV. He became king in 1648 after he signed a charter greatly restricting the royal authority. But the power of the nobles was soon undermined by charges of improper self-enrichment against their leaders, many of whom were forced to leave the country. In 1657 Frederick began a war against Sweden to regain provinces lost by his father. He was defeated and in 1658 signed the Treaty of Roskilde, ceding a portion of Norway and some Danish islands to Sweden. Shortly after the conclusion of peace the Swedes reopened the war and besieged Copenhagen. With aid from the German region of Brandenburg, the Danes expelled the Swedes from the Jutland Peninsula. In 1660, however, deserted by his allies, Frederick was obliged to make peace, relinquishing all claims to the territories possessed by Denmark in southern Sweden. In that year both the commons and the clergy agreed to the transformation of the kingship from an elective to an absolute and hereditary monarchy.