During the greater part of the Middle Ages, Denmark was the leading Nordic country. The Kalmar Union, which was established at the end of the 14th century, made Denmark one of the most influential countries of Europe. In Europe, Denmark was the most densely populated country. About one million people lived there, as many as in Norway and Sweden put together.
Few peasants were land-owners. They leased their farms from the nobility or the Church. Only one in ten peasants was a free-holder with land of his own.
Many peasants were heavily dependant on their land-lords and had to do labour at the estates of the noblemen.
During the 13th and early 14th centuries, the aristocracy became more powerful. The King ´s position weakened. Around 1330, more or less the entire country was in the hands of noblemen, many of them German counts from Holstein. Skåne (Scania in English) and Blekinge were sold to Sweden. After becoming King in 1340, Valdemar Atterdag strengthened his kingdom, recaptured Skåne and Blekinge and conquered the islands of Öland and Gotland, all within a few decades.
Denmark and Norway were united in 1380. In 1389, Sweden joined the Union which was ruled by Queen Margareta. The Union was officially established in Kalmar in 1397. Denmark became the leading country of the Union. Most bailiffs at the Royal Castles were Danes. Öresund, with the rapidly growing town of Köbenhavn (Copenhagen in English), was the centre of the Union.
Sweden left the Union in the middle of the 15th century. Denmark tried to re-establish it on several occasions but without much success. However, the bond with Norway lasted until 1814.