The raids are related to the settling of Poles in Lithuania. Apparently, it was in the second half of the 13th century that the first Polish individuals (or perhaps a few Polish families) settled down in Lithuania permanently after Lithuanians began intensifying their incursions into Polish territories. Polish historians have established that Lithuanians could possibly seize up to 500 or 600 captives during a single larger-scale raid. Taking into account the number of incursions into Poland, historians presume that Lithuanians might have captured about 12,500 Poles whom they subsequently brought back home. The process went on until 1376, the year of the last major raid into Poland by Lithuanian troops.
Medieval trade in humans
Lithuanians would mostly capture women and children. The enslaved women used to become wives, housekeepers or nursemaids. The captured Polish children would become part of the unfree family in the homes of the nobility. Lithuanians were also used to selling or exchanging some of the captives within the human trade networks of the time. It seems that Lithuanians were little interested in ordinary men whom they usually tried to kill on the spot. If left alive, they would have caused problems and would have required vigilant guarding. The low level of agriculture in the Lithuania of that time did not call for more working hands that their owners would have needed to feed. Lithuanians were more interested in the men whom they were able to exchange for a good ransom. Lithuanians had captured but later freed the duke of Masovia Konrad II (1264), the duke of Dobrzyn, Siemowit, who was the brother of Wladyslaw Lokietek, the future king of Poland (1295), and Ubyslav, the son of the castellan of Brest (1295). The father of the latter was compelled to sell a village in order to collect at least 20 kilograms of silver as a ransom for his son who had spent three years in captivity. And there are more similar examples.
Poles were unable to make their communities more numerous and compact, because the captives had no rights whatsoever and were subject to human trade. On the other hand, the Lithuanian nobility would share the captive Poles among themselves as war booty. This is why Poles eventually could be seen in various corners of Lithuania.
An example is the expedition of the German Order in May 1290 led by Erneke, the komtur of Ragnit. When the crusader ships passed the confluence of Nemunas and Neris, Lithuanians devised a plan aimed at taking them by surprise. "Finally everybody agreed that one of them, who could speak Polish, would dress as a woman and, standing on the bank of Nemunas, would ask the crusaders to take him on board of their ship as they pass by as if to save him from the captivity of the infidels." The plan worked and the crusaders who decided to save the "woman" all died. The gullibility demonstrated by crusaders indicates that captive Polish women were quite common even in the western part of the Lithuania at that time. Raids of plunder into Polish lands and communication with captive people helped a few Lithuanians learn Polish.
Poles in Lithuania: captives, fugitives and missionaries
In the 14th century, the new developing cities, such as Kernavė and Vilnius, offered an attractive environment for the few foreigners who decided to settle down in Lithuania. The fact that Gediminas, the Grand Duke of Lithuania, asked Franciscans to send monks to Lithuania who knew Polish is an indication that Poles living in Lithuania, not necessarily in Vilnius, required someone to take care of their souls.
Trying to compare trade ties between Riga, Lithuania and Polish lands, one can easily notice that Lithuanians traded with Poles considerably less actively than the citizens of Riga did. We know of just two documents mentioning business relations between Polish merchants and their counterparts in the Grand Duchy of Lithuania. One of them is the 1371 papal bull referring to trade ties between Masovians and Lithuanians; the second one is the 1383 privilege issued to merchants from Lublin by Jogaila, then the grand duke of Lithuania. The two documents reveal that trade contacts existed, although they provide no information about the Poles living in Lithuania of that time.
There were some individual cases, but they would occur very seldom and in quite specific circumstances. For instance, brothers Pawel and Rostk fled to Lithuania together with their wives and children in the early 14th century after committing a grave crime in their motherland. In this context, Polish captives should be put in line beside people involved in criminal offences, individuals arriving alone, for instance, in Vilnius, and participants of the Franciscan missions. Although multinational, the missions could include Poles as members of the teams visiting Lithuania. Until the middle of the 14th century, evangelisation efforts by Franciscan monks were related mostly to Livonia, but later they started working actively in Poland and the Black Sea region. It was not a coincidence that the king of Poland Casimir III the Great noted in his letter to the pope in the middle of the 14th century that pagans living in neighbouring lands of Rus and the GDL listen eagerly to Franciscan sermons. The latter reference is true speaking of both Tatars and Lithuanians. The phenomenon of "listening" to sermons leads to the presumption that the missionaries could speak the languages of local peoples.
The number of such missionaries could not be high, but they were building foundations for a better mutual understanding and smoother communication. The Christianisation of Lithuania in 1387 offered better conditions for permanent life in Lithuania, first of all in Vilnius, for Polish (as well as Czech and German) clergymen and monks. All newly Christianised countries had to live through the period when foreigners dominated the ranks of their clergy, simply because they were unable to bring up their own priests immediately after the conversion to Christianity. Throughout the whole country, the number of Polish missionaries was very insignificant and was not able to influence key demographic characteristics. Historical sources never mention any quantitatively significant migration of Poles to Lithuania during later centuries as well. Therefore, the polonisation of Lithuania, which took place from the 16th century through the 18th century and later, should largely be linked with cultural and ideological processes rather than with economic and social ones.