The Poles forced their enemies to besiege fortified areas, thereby compelling them to disperse and, consequently, weakening them. At the same time, they waged what was known as guerrilla warfare, consisting of maintaining constant combat contact with enemy forces and eliminating units separated from the main forces. The fortified areas of the Osiecznica municipality, which were also naturally protected by their location, were conducive to precisely this kind of warfare.
During the Polish-German war of 1015–1018, the municipality’s territory was an area through which both Polish and German armies passed. At that time, virtually all settlements in the area were burned and destroyed. The local population took refuge in inaccessible forests.
In 1039, these lands suffered another catastrophe caused by the invasion of Silesia by the Bohemian duke Bretislaus, who took advantage of the weakening of the Polish state to seize Silesia. Since the people living in these areas were not yet closely connected with the central administrative authority of the Polish state at that time, they accepted the new rulers without much resistance.
The castellany of Bolesławiec, including the territory of today’s Osiecznica municipality, returned to Poland again in 1050 after the fierce battles fought by Casimir the Restorer against Bretislaus. Once again, the local population suffered as a result of this war between the dukes.
During the period of the renewed flourishing of the Polish state, the castellany of Bolesławiec, including the defensive manor in Kliczków, played a significant role in resisting the ambitions of Bohemian dukes and German magnates.
During the reign of the Polish duke Bolesław the Tall, part of the municipality’s territory, probably including the villages of Kliczków and Osieczów, was granted to monasteries, but was later bought back by the count of the Bolesławiec castellany.
In the 12th and 13th centuries, free peasant settlements began to disappear in this area; individual settlements were transferred to knights and monasteries.
At the beginning of the 13th century, villages began to be founded under German law. The village of Ławszowa received such a foundation in the 13th century. Some chronicles even give the exact foundation date of Ławszowa, known in German as Lorenzdorf or in Latin as Laurentii Villa, as 1233.
During this period, the village had approximately 300 inhabitants, including settlers and serfs. It was therefore one of the largest settlement communities in the area and effectively served as a market village. A church was built in Ławszowa as early as 1376; it was later burned and destroyed several times, including during the Hussite Wars.
The village of Kliczków can boast an equally early foundation as Ławszowa. A castle was erected here as early as 1297 and became the property of Bolko I, Duke of Świdnica-Jawor. A number of craftsmen working for the castle settled around it. At the beginning of the 14th century, the settlement around the castle was called Kliczdorf; this name presumably dates from 1305. At the beginning of the 15th century, specifically in 1417, a second name for the settlement was recorded: Kliczdorff. A church was built in Kliczków half a century earlier than in Ławszowa, as the first references to it date back to 1305. The masonry church was founded in 1417, presumably by Duchess Anna, the wife of Charles IV, who at that time owned Kliczków Castle. After Duchess Anna’s death, Kliczków Castle passed into the hands of knightly families.
At that time, Kliczków Castle was one of the more important castles in Silesia. Its library was a rarity among castles in the area—it was then one of the largest book collections.
The village of Tomisław received its foundation charter somewhat later, although the origins of the settlement date back to the beginning of the 14th century. Thommendorf, Thomosdorf and Thomodorf were the German names of this settlement.
The church in this settlement was built in 1346 and belonged to the deanery of Lubań within the nomenclature of church administration. Tomisław, as a village under German law, was created by merging two settlements located nearby, on the left bank of the Kwisa River.
The village of Osieczów has a history as distant as those of Ławszowa, Kliczków and Tomisław; in German it was called Aschitzau. It was established in the 13th century, and the first references to it date from 1476. In later periods, the settlement changed its name several times, successively bearing the names Aschitcaw, Assesaw and Aschieczan. This village was subordinate to the Bolesławiec castellany and was directly connected to it by a road.