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King Niels (1104-1134), had started a war against the Vendian prince Henrik and as Møn lay in an unfortunate position and was well known for being a wealthy island because of the herring fishery, it suffered a lot of plundering during that time. The war and the plundering however stopped as prince Henrik was defeated by King Knud Lavard but only for a short time as Kund Lavard were murdered in 1131 and then the next king in line, Erik the 2nd Emune (1134-1137), imidiatly started a new war against the Vendians. Even the next king, Erik the 3rd Lam (1137-1146), went on a warfare against the Vendians but it never developed into a real fight. First when king Valdemar the Great (1157-1182) became king, the Vendians were defeated and their reign in the Baltic region was broken.
One of the men who stood closest to Valdemar was Absalon. Absalon owned Elmelunde Castle and lived a lot on Møn, he often took to raids against the Vendians from Grønsund, which at that time was a common gathering place for the Danish navy. The Vendians hated Absalon as he was observant and brave and combined the two skills wisely. An attempt of conquering Absalons fleet was however made at one time when Absalon himself was busy taking care of a conquered fleet near Rügen. The Vendians had planned a landing at Grønsund with their cavalry and the foot troops would land on the north coast and the fleet itself would be at Keldby Nor. But they failed, Absalon heard about their plans and hurried home. Absalon sent a fleet to Koster that was to wait until the Vendians´ fleet had gone into Keldby Nor. If he could not defeat them there, it would be the Vendians only escape route. The Vendians however waited for quite some time with their attack and Absalon sailed down to Falster where he sent out two ships to find out what the Vendians were up to. One ship only had men from Falster and the other only men from Zealand. After Absalon had returned to Koster, a man named Gvemme invited the men from Falster to a party where they got drunk and could not scout as Absalon had ordered them to do. Gvemme was a good friend of the Vendians and frequently reported the whereabouts and activities of the Danes, he was also onboard the ship with the Zealandic crew, so instead of scouting he was gathering information to the enemy. When the Vendians were ready to attack they sent men ahead to go and visit Gvemme and get the latest news, but unfortunately Gvemme was not at home when they came, as he was posted on the Danish fleet, and when the servants learned what was going on they warned Absalon. As the Vendians´ plan now was uncovered, they gave up and sailed into Grønsund and destroyed a crucifix the people of Møn had raised there. They would also have attacked the drunken men from Falster if they had not been warned in the last minute by a scoutship from Zealand, which in its turn only barely got away from the Vendians. When Absalon got the news that the Vendians were on their way, he sent out two scouts from Bogø to find out what they were up to, but he did not have any patience and he sailed after the scouts, not waiting for the rapport. He knew the strategy of the enemy too well: attack in the break of dawn, quickly settle the battle and take off as soon as possible. Absalon did not want to be late... When the Vendians saw Absalon´s ships at daybreak they fled and only a terrible storm stopped Absalon from following them. Absalon sought shelter on Falster but the Vendians who had trouble getting away only using the oars, set sail on one of the ships, which capsized and the men drowned. Two ships managed to escape using only the oars only to be captured by prince Jarimar of Rügen. The prince sent one of the ships back to Absalon in reward, because Absalon had made it possible for the prince to capture them in the first place. As this happened on the 6th of December = St. Nicholas day, the Vendians thought he protected Møn and Denmark and did not dare to attack Denmark again!
From the middle of the 12th century and up to the days of King Frederik the 3rd (1648-1670) Møn was a Crown property and was managed by a feudal lord. Møn was so highly ranked as a county that only Denmark's highest noblemen were put to rule over it. For his help the feudal lord had a forest officer who was in charge over collection duties and goods, arranging parties and hunts for prominent people and even kings who visited Møn. The forest officer also had to care for order to be upheld in the region. These prominent visits were not very welcome to the ordinary people (and might not even for the host himself) as they often came with a big party who were to be fed and housed preferably in a mansion or a castle, they would dry out the stock of meat and corn and move on to the next county. The feudal lord had full authority to judge in any legal questions, fights or disagreements of any sort and care for matters to be taken to a court if necessary, but most of the time he would pass on this authority to his forest officer who then got a powerful position over the ordinary residents. But not all of the feudal lords or forest officers terrorized the common people there where also those who loved both their king and county.
During the reign of Valdemar the Great's sons Knud (1182-1202) and Valdemar the 2nd (1202-1241) Møn was a calm and happy land as no wars effected it and the Vendians kept their distance.