merchants and artisans quickly assimilated and were Polonized. The majority of the Lithuanian nobles spoke the Polish language, however they never considered themselves Poles and the Union of Lublin was only signed during the second attempt in 1569, with the agreement that both states will be sovereign entities within the Commonwealth. Their opinion did not change within the union and was confirmed again in the Reciprocal Guarantee of Two Nations in 1791. Over the centuries, the composition of the population of Vilnius changed to become ethnically less Lithuanian. According to historian Vytautas Merkys, the city lost a great deal of its old population during the brutal rampages of the Swedish and Russian armies in the 17th and 18th centuries, and they were replaced by the newcomers, however the Lithuanians also constantly inhabited in Vilnius. According to the Russian Empire Census of 1897, only 2.1% (3200 residents) identified themselves as Lithuanian-speakers, while the speakers of Polish language (30.8%; 47,600 residents) and Yiddish (40.0%; 61,800 residents) were the largest linguistic groups of the city. According to the Parish censuses of 1857–1858, the Lithuanian population remained significant in the Vilna Governorate and, according to different authors, was between 23.6% and 50.0% (210,273–418,880 residents). Among the Szlachta (nobility) in Vilnius during the census of 1897, there were 5,301 (46.3%) local nobles and 6,403 (54.7%) newcomers, of these 24.1% noble newcomers came from Vilna Governorate territories, while the rest of newcomers nobles came to Vilnius from Grodno Governorate, Minsk Governorate, Vitebsk Governorate, Kovno Governorate, Vistula Land and other regions. Ethnic Lithuanian numbers in the city of Vilnius reached record lows in 1931 (1600 residents – 0.8%, while Poles accounted for 65.9% – 128,600 residents) following the 1922 annexation of Vilnius Region by Poland and the Lithuanians retreat from the region to the temporary capital of Kaunas. Following the Soviet–Lithuanian Mutual Assistance Treaty in 1939, Lithuania regained one third of Vilnius Region and made efforts to Lithuanize Vilnius by the introduction of Lithuanian laws. Prime Minister Antanas Merkys once said that it was intended "to make everybody think like Lithuanians. First of all, it was and still is necessary to comb out the foreign element from the Vilnius Region". The Lithuanian Government put into force a law according to which "who on 12 July 1920 (...) were regarded as Lithuanian nationals, and on 27 October 1939 were resident in the territory became Lithuanian nationals" (this definition