Until the year 1700 the Danish army consisted of paid volunteers, mostly foreigners, who were fighting to help Denmark recover lands they had lost to Sweden in war. The most important piece to them was Skåne, the southern part of Sweden, because that meant they owned both sides of the Sound and could charge fees to ships desiring to trade with the Baltic countries. They were unsuccessful at retaking the land, though, and their wars were costing them money they were no longer receiving from trade ships, so they had to change to a different system.
Beginning in 1701 and again in 1733, the paid mercenaries were joined by the national militia. This militia was made up of a number of Danes drafted from the farms throughout Denmark. A law was passed in 1733 that gave large landowners a number of responsibilities, one of which was deciding who would serve in the national military. The law required these landowners to supply the militia with a certain number of men from among their renters, so most of those who served in the national militia were sent by the landowners. Not many records created by the landowners during this period were preserved.
In 1788 the Stavnsbåndet was passed, basically changing the position the landowners had over their peasants. Included in this change was the fact that landowners no longer had a say in who was to serve in the military. Instead, the country was divided into levying districts (lægds) and the largest landowner was put in charge of keeping a list of all young men living within his boundaries. The exceptions of those who were to be listed were sons of nobility, large landowners, ecclesiastical priests and clerks, schoolteachers, and other prominent members of the area.
At the time of their registration, males were entered on the levying roll in the district in which they lived and assigned a specific number, which got lower as they got older. This number determined when they would be called to action if they were needed to fight for their country. The number also enables a genealogist to follow a male either forward in time or back in time.
The age from which a person had to be registered with the district changed over the years. When the registration system officially started in 1788, all males from birth to age forty-four were recorded in the levying district. This continued to 1849 when the ages of registration spanned either from when a boy was confirmed or turned fifteen, to thirty-eight. After 1869, males were not added to the rolls until they were seventeen years of age. If a man became unable to serve because of bad health, added responsibilities, or other legitimate reasons, they were dropped from the roll before the customary release time. Any time this happened an indication was made on the rolls themselves and they stop appearing in succeeding rolls, unless they had sons also registered.
The significance of the Danish military levying rolls is what the officials recorded and the time period for which they are available. The rolls list the father's name, child's name, age, place of birth (not always a parish name), current residence, height, and old and new number on the rolls. If a person moved, they were crossed out on the regular roll and an indication of where they went can be found underneath the original entry. Many times these moves were to other counties, so they are very helpful in determining the movements of a family. Since these records are generally available from 1788, they can be helpful for even research into the mid- to late 1700s.
Occasionally you will find a family that moved, but the person failed to record the place they moved to and their new number there. If you are working back in time, that should not be a problem because you also have the place of their birth. All you need to do to get around this omission is to go to the district in which they were born and look up the levying roll taken after their birth and continue forward in time from there.
The Danish military levying rolls can be accessed from the Family History Library in Salt Lake City, generally from 1788 to 1860. The registration system was continued until World War II, so if you need a later one that is not available from the library, you would need to contact or travel to the regional Danish archive in which your specific records are being kept.