[4] When King Valdemar IV of Denmark and his troops invaded Gotland in 1361, they met the first line of resistance at the Battle of Mästerby.

A great number of archeological finds have been made here along with grave fields, stone mounds and traces of houses dating from the Bronze, Iron and Viking Ages as well as from Medieval times.

[11][13] The courthouse for southern Gotland was situated at Mästerby, along with a gallows and a place for corporal punishment from 1000 until the end of the 16th century.

The Danes tried to cross the stream, but that proved to be a tactical error since the banks were very steep, which made it hard for the heavily armed soldiers to advance.

The failure of the plan resulted in a massacre, about 1,500 Gotlandic farmers and other local inhabitants being killed by the Danish invaders.

The legible text is Anno Domini MCCCLXI (Roman numerals for "1361") and finally the word Iacobi (Latin for Saint Jacob and his day in the calendar).

[16] A priest in Mästerby parish, Hans Nielssön Strelow, wrote the Cronica Guthilandorium ("Chronicle of Gotland") in 1633.

[17] Historians realized that it was unlikely that King Valdemar would have honoured his fallen enemiesm but the battlefield team from the Swedish National Heritage Board, the archeologist Maria Lingström and the Mästerby History Society decided to investigate if there was any truth to the legend.

The distribution and nature of the finds indicate that the main battle occurred in a sandy part of the mire, where Danish troops crossed and advanced on Mästerby.