Although towns often had this character of ethnic islands [in colonized regions like Wales and Eastern Europe], they rarely attained complete racial homogeneity. Native populations lived within the walls, sometimes in the humble position of manual labourers, sometimes as artisans or even merchants. The expanding urban economy of the twelfth and thirteenth centuries seems to have allowed both immigrant and native to prosper. The picture darkens as the recession of the later Middle Ages begins. As the meal shrank, the diners began to eye each other more suspiciously.
One consequence of the dynastic uncertainties in eastern Europe during the later Middle Ages was that the German burgess population had a far more complicated and demanding political course to steer. […] In the early fourteenth century, during the dynastic manoeuvring that culminated in the revival of the Polish kingdom under Wladyslaw Lokietek, the German burgesses of Cracow made a serious miscalculation. They backed first the Luxemburg, then a Silesian aspirant, rather than Lokietek, were abandoned by their allies, and suffered savage reprisals, which took the form of a racial persecution. […]
[…] The Krasiński Annals add the detail that ‘anyone who could not pronounce soczewic [should be soczowica — see comments] (lentil), koło (wheel), miele (grinds) and młyn (mill) was executed. The application of this shibboleth gave events a starkly ethnic-linguistic imprint. This linguistic chauvinism manifested itself in another development of the same year. On 18 November 1312 the official records of the city of Cracow, which until that time had been kept in German, began to be written in Latin. […] The exclusion of the German language clearly reflects the anti-German pogrom of that year. Its replacement by Latin rather than Polish reminds us how undeveloped this vernacular was as a written idiom. (Similarly, when Old English disappeared from documents such as wills and writs after the conquest of England by a French-speaking aristocracy in 1066, it was Latin that replaced it. Eleventh-century French, like fourteenth-century Polish, had not yet won the esteem of a language of official record.) In the century following the rising of 1311-12, Cracow was gradually Polonized. […] [By 1470] Cracow had become a Polish city with a German minority rather than a German city in Poland.