In all the three Scandinavian countries leiðangr evolved to a tax, paid by all (free) farmers until the 19th century. As the clergy and the noble estate were exempted from this tax burden, the tax came to facilitate the Church's and the noble manor's acquisition of land. In the end the states became increasingly dependent on the nobility for defence and warfare.
The leiðangr was a system organising a coastal fleet with the aim of defence, coerced trade, plunderings and aggressive wars. Normally, the fleet levy was on expeditions for two or three summer months. All free men, i.e. the peasants, were obliged to take part in or contribute to the leiðangr. All of the leiðangr was called to arms when invading forces threatened the land. In the expeditions only a faction of the ships were taking part, but as the expeditions often were profitable many magnates and chieftains tried to join with their people as often as possible. In the 11th century the leiðangr was very successful. Sections of the Danish and Norwegian leiðangr conquered Western England under Canute the Great, mainly a re-conquest of the Danelaw.
The lands were divided into districts, ship's crews, "skipreiða" (Old Norse), "skipæn" (Danish) or "roslag" (Swedish). The farmers of the district had to build and equip a rowed sailing ship. The size of the ships was defined as a standardized number of oars. In Norway, there were 279 such districts in 1277, in Denmark two-three times as many. The head of a district was called "styrimaðr" or "styræsmand", steersman, and he functioned as captain of the ship. The smallest unit was the crew of peasants who had to arm and provide for one oarsman ("hafnæ" in Danish, "manngerð" in Old Norse).
The weapons the ships would carry were typically: bows, spears, swords, battle- axes and shields. In the 11th century, jarls are mentioned as the chieftain of the leiðangr, in the 12th century the bishop was head of the fleet levy.