Polish claims on Wilno/Vilnius

[michael mills]

The Polish claim to Vilnius before the Second World War, based the ethnicity of the majority of the population, was morally undermined by Poland's refusal to apply that same principle in relation to other regions that it had taken possession of on the basis of an historical claim.

[Piotr Kapuscinski]

Poland's refusal to apply that same principle in relation to other regions that it had taken possession of on the basis of an historical claim.

One of regions in your mind is Eastern Galicia.

However, you should take into account that Eastern Galicia was undergoing rapid Polonization before WW1 (despite Austrian attempts to promote Ukrainian national identity), Polish leaders therefore expected that it was soon going to become a majority-Polish region.

Indeed, analysis of data from Austrian censuses between 1880 and 1910 for languages in Eastern Galicia (in %) confirmed that trend:



Between 1880 and 1910 Polish-speakers in Eastern Galicia increased from 27,93% to 39,75%.

Percent of Ruthenian-speakers in Eastern Galicia declined from 64,74% to 58,92% in that time.

Percent of German-speakers also declined from 7,21% to 1,21% during those thirty years.

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If we look at religions then % of Roman Catholics was also increasing between 1880 - 1910, though not as fast as that of Polish-speakers.

One of several reasons for that growing percentage share of Roman Catholics, were numerous conversions to Roman Catholicism.

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In 1910 Western Galicia, contrary to eastern part, had an absolute Polish-speaking majority of 96% (ca. 2,56 million).

Entire Galicia (West + East) had 58,6% Polish-speaking majority (ca. 4,7 million out of a population of ca. 8,0 million).

Below is the data for Eastern Galicia by county (red squares = counties with Polish-speaking majority in 1910):

Click the image to enlarge it:

Primary source for this data is:

Oesterreichische Statistik, N.F., Bd.1, H.1: 1910

[Piotr Kapuscinski]

I know topic is about Vilnius not Danzig, but here are some numbers:

Freie Stadt Danzig census from 1923 shown 327,827 Germans.
http://en.wikipedia.org/wiki/Free_City_of_Danzig

When Polish administration got there in mid-1945 they counted 123,932 Germans.
Expelling started in July and by January 1946 were 39,497 Germans left.
http://www.zdsk.pl/historia/4-wysiedlen ... -1945-1947

Not sure how many Germans were there in 1939 or 1944, but to me looks like advancing Soviet army did much better job than Polish administration...

Let's remember that the German 1923 census - like Austrian censuses of 1880 to 1910 - counted language, not national identity.

The city was dominated by German language, therefore many people who lived there and did not consider themselves as Germans also had to be fluent speakers of German language (the same was the case in Galicia under Austrian rule, where Roman Catholics who lived in areas dominated by Rusyn language often spoke Rusyn but identified as Poles, while Greek Catholic peasants who lived in areas dominated by Polish language often spoke Polish but sometimes identified as either Old Rusyns or - if already influenced by nationalist ideology - as Ukrainians).

According to Polish census of 1950 in the City of Gdansk there still lived 22,213 autochthonous (pre-war) inhabitants of this city, who declared Polish ethnic-national identity (this number does not include Germans who were not expelled). Add to this 7,127 similar pre-war inhabitants in the county of Gdansk and 2,209 in the City of Sopot (both of which were also parts of the pre-war Freie Stadt). In total 31,549.

This 31,549 includes only those who lived in the same county in 1950, as in 1939. If someone lived in Danzig in 1939, but in Sopot in 1950, then he is not included among them (even though both counties lie within the pre-war Freie Stadt Danzig). There were 3,164 more autochthons Poles who between 1939 and 1950 migrated between counties either within the former Freie Stadt (for example from Danzig to Sopot) or from other nearby former German areas - namely counties of Stuhm, Marienburg, Marienwerder, Lauenburg, Landkreis Elbing and Stadt Elbing - to Gdansk or Sopot. This 3,164 includes 828 who came to City Gdansk, 1112 who came to City Sopot and 1224 who came to Gdansk county.

In total up to 34,713 pre-war Poles from FS Danzig. Let's say 34,000 assuming that 700 were immigrants from Stuhm, Marienwerder, Elbing, etc.

But 34,000 still does not include Polish families from pre-war Free City Danzig who stayed in Poland after WW2 but migrated to other counties. For example ethnic Poles who lived in Danzig in 1939 but later moved to Wrocław, Warsaw, Cracow, Szczecin, Poznan, etc. - where they lived in 1950 - aren't included in this number. So the real number of pre-war Poles from FSD in entire Poland in 1950 was perhaps even higher.

These two numbers given above - 31,549 and 34,713 - are over twice as high as the number of Polish-speakers in FS Danzig according to 1923 census. And we must remember that many Poles from Danzig fled from the advancing Soviet army before mid-1945.

Perhaps Poles were not escaping on such a massive scale as Germans, but many ethnic Polish citizens of Germany also fled westward from the Red Army and from Communism. According to wartime memoirs of my family, a common opinion among Polish people was that the Red Army was more barbarous than the Wehrmacht. When the Wehrmacht retreated from the town where my grandfather lived in 1945, they even allowed local civilians to take the rest of their food supplies (as they were unable to evacuate all of it). But when the Red Army came a few days later, they confiscated all that food. It was taking place in the region of Greater Poland, in areas which belonged to Poland before WW2.

Memoirs of my family also include Soviet soldiers stealing watches and other things from civilians. Nothing about rapes, though.

But Red Army's behaviour towards ethnic Poles in pre-war German territories was much worse than in Greater Poland.

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All of this shows that the number of Poles in Danzig in 1923 must have been at least 2 - 3 times higher than official German cesus data admitted.

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This map shows territorial origins of population of former German areas given to Poland, as of year 1950.

Dark red shows pre-war citizens of Germany who were not expelled and in 1950 lived in the same county as in 1939.

Light red = pre-war citizens of Germany who weren't expelled but migrated between counties, within former German areas.

Click the map to enlarge it:

Area marked as E are former German lands incorporated into Gdansk Voivodeship after WW2. This area includes Free City Danzig and other West Prussian counties mentioned above (as well as Lębork county in Pomerania). In 1950 it had a population of 500,846 including 50,843 autochthons who did not migrate between counties as well as 5,238 autochthons who did migrate between counties within that area (for example from Sztum to Sopot, etc.) and 1,427 more autochthons who moved from other former German territories (A, B, C, D, E, F, G, H, J).

In total pre-war German citizens comprised 57,508 people in that particular area - or 11,5% of its population.

Another 63,301 people in area E were those who moved from nearby counties of pre-war so called "Polish Corridor" (light orange).

[DarthMaur]

Maintaining ethnic diversity overall enriches the whole and I am glad to say that the majority of modern Danzigers I meet are proud of their city's roots - Polish, German and Free City in similar measure.

How many of those Danzigers are descendants of the German inhabitants of the city who comprised the overwhelming majority before the Second World War?

The situation is that the German population of Danzig was entirely expelled in 1945 and replaced by Poles brought in from elsewhere. Only ethnic Poles were allowed to remain.

By contrast, not all ethnic Poles were expelled from Vilnius, which still has a substantial Polish minority, as Polish members of this Forum often remind us. That contrast suggests that Poles were more ruthlessly efficient in expelling Germans from Danzig than Lithuanians were in expelling Poles from Vilnius.

So far as I know, the present population of Danzig is entirely of Polish ethnicity, so there is no ethnic diversity there, unlike the situation in Vilnius.

It is a bit more complicated. Not every person with German links (for lack of better term) was expelled from the territories Poland got after WW II. Many of them left in the 1970s, heading to Germany. A capitalist wealthy Germany, as opposed to leaving from communist Lithuania to communist Poland.

Afaik, Potsdam population agreements called for resettlement of both Poles and Germans from territories that were to change hands. It is possible that it was applied more thoroughly to the German population, indeed, given the context i would not find that surprising.

[Piotr Kapuscinski]

not all ethnic Poles were expelled from Vilnius, which still has a substantial Polish minority, as Polish members of this Forum often remind us. That contrast suggests that Poles were more ruthlessly efficient in expelling Germans from Danzig than Lithuanians were in expelling Poles from Vilnius.

The main reason why so many Poles were allowed (sometimes even forced) to stay in Lithuania was because Lithuania lacked the surplus of ethnically Lithuanian population necessary to re-populate areas cleansed of Polish population. The same was the case in Belarus.

Even after that limited expulsion of about half of the Polish population, much of the deported population had to be replaced by ethnically Russian immigrants. And so Lithuania not only failed to get rid of its Polish minority, but also acquired another "problematic" minority.

Poland by contrast apparently had enough ethnic Poles to re-populate areas from which Germans got deported, even without bringing westward all of ethnic Poles from eastern Polish territories annexed by the Soviet Union, since a few million Poles remained in those areas.

[Piotr Kapuscinski]

After deporting Germans and repopulating the land in 1945-1958, Poland still had a considerable excess of "manpower" available.

Official data from Soviet 1959 census counted 1,380,282 ethnic Poles in the Soviet Union:

http://demoscope.ru/weekly/ssp/sng_nac_59.php

Belarusian SSR - 538,881 (including 332,300 Poles in Grodno Oblast)
Ukrainian SSR - 363,297
Lithuanian SSR - 230,107 (including 191,365 in the area of Vilnius)
Latvian SSR - 59,774 (mostly in areas of Daugavpils and Ilūkste)
Rest of the SU - 188,223

Official data from Czechoslovakian 1950 census counted also a significant Polish minority:

http://en.wikipedia.org/wiki/Ethnic_min ... mographics

Czechoslovakia - 70,816 (including 59,005 in the area of Zaolzie)

So even if data from those censuses did not under-report the number of Poles (counting some Poles as Non-Poles, which most likely was the case), then Poland still did not use around 1,500,000 potential settlers that were available, if the Soviet Union agreed to let them go.*

*That was a problem, as in many cases authorities of Soviet republics - fearing depopulation (as they did not have enough people to replace expelled Poles - apart from ethnic Russians**) - did not allow many Poles to go. That was especially applied to Poles who lived in the countryside, who were considered "less Polish" and Soviet authorities hoped to Russify / Belarusianize / Ukrainize / Lithuanize them in near future.

**In Soviet republics such as Lithuania and Belarus many deported Poles were replaced with Russians, not with titular nationalities.

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Ethnic groups of Zaolzie 1880 - 2001 (Polaci = Poles, Nemci = Germans, narodnost slezska = Silesians, narodnost moravska = Moravians):

http://www.polonica.cz/content/Polaci%2 ... sinsku.pdf

During 100 years the region of Zaolzie in Czech Republic changed from 80% Polish and 10% Czech to 80% Czech and 10% Polish.

[Piotr Kapuscinski]

Just a general comment:

The Polish claim to Vilnius has been based on essentially the same criterion as the former German claim to Danzig, ie the majority of the population being ethnically Polish and German respectively.

The Lithuanian claim to Vilnius was essentially based on the same criterion as that of the Polish claim to Danzig, ie prior ownership, Vilnius being originally inhabited by Lithuanians and Danzig by Poles (or at least Slavs related to Poles).

As a result of the Second World War, Vilnius has returned to Lithuanian sovereignty and Danzig to Polish. The best course in my opinion would be to leave that situation as it is.

The fact that there is today a considerable ethnic Polish minority in Vilnius suggests that Lithuania has been less ruthless in removing the Polish population of that city than Poland was in removing the ethnic German population of Danzig.

The difference being that Balts of Vilnius were peacefully Polonised, adopting Polish language, culture and identity - and becoming Poles. By contrast, Slavic population of Gdansk was massacred by Teutonic Knights and then replaced with German settlers.

Pope Clement V wrote in years 1310-1317 about Pomerelia and Gdansk:

1) Original Latin text:

"Novissime vero ad nostrum pervenit auditum, quod dicti praeceptores et fratres hospitalis eiusdem dilecti filii nobilis viri Wladislai Cracovie et Sandomirie ducis terram hostiliter subintrantes in civitate Gdansco ultra decem milia hominum gladio peremerunt infantibus vagientibus in cunis mortis exitum inferentes, quibus etiam hostis fidei pepercisset. 
(...)
Gravem dilecti nobilis viri Wladislai ducis Polonie querelam accepimus, continentem, quod magister et fratres domus s. Marie Theutonicorum non attendentes, quod quondam Conradus dux Polonie avus eiusdem ducis eosdem magistrum et fratres, quos veros credebat katholice fidei defensores, ad partes illas pro defensione ipsius fidei primitus advocavit et nonnula inmobilia et mobilia bona liberaliter concessit eisdem, alias eos dictus Conradus et successors sui benigne ac favorabiliter prosequendo; sed ipsi dicto duci se reddentes ingratos et ad bona ipsius rapacitatis manus extendentes, illicite ducem ipsum terra sua Pomoranie Wladislauiensis dyocesis, que de regno Polonie fore dinoscitur temeritate propria spoliantes, illam cum hominibus, vasallis, castris, villis, possessionibus et bonis existentibus in eadem contra iusticiam occuparunt et detinuerunt iam per octo annos et amplius sicut adhuc detinent violenter, fructus ac redditus et proventus provenientes ex illa percipientes indebite et iniuste, illam sibi reddere contradicunt in ipsius ducis grave dispendium et regni predicti diminucionem enormem et scandalum manifestum."

2) And English translation:

"It has recently come to our attention that the said preceptors and brothers of the Teutonic Order, stealing into the land of our dear son, the nobleman duke Vladislav of Cracow and Sandomir, in a hostile manner, killed more than 10,000 people in the town of Gdansk by the sword, inflicting death upon infants crying in their cradles, whom even the enemies of the faith would have spared. 
(...)
We accepted the serious complaint of our dear son, the nobleman Duke Vladislav of Poland, the master and brothers of the Teutonic Order not being present, maintaining that the late Duke Conrad of Poland, grandfather of the same duke, first called the master and brothers, whom he believed true defenders of the Catholic faith, and he freely conceded to them some movable and immovable goods, and the said Konrad and his successors with benign favour followed these up with others. But, showing no gratitude to the said duke and extending the hands of rapacity towards his goods, they boldly and illicitily robbed that duke of his own land of Pomerania, of the diocese of Wloclawek, which it is known should belong to the kingdom of Poland, along with the men, vassals, castles, villages, possessions, and goods in it, now occupying and detaining it against justice for eight years and more still violently detaining its fruits and revenues and produce wtihout right and unjustly, they refuse to return it to him at great cost to the duke himself and immense damage to the aforesaid kingdom and in manifest scandal."

The longer quote is from Lites I (3), 69 (Papal bull).

[4thskorpion]

Vilnius:The Jewish population of Vilna swelled to roughly 63,000 (41% of the total population) in 1897, to 76,000 in 1901 (46%), to 85,000 in 1903 (52%), and to perhaps as many as 100,000 in 1905 (51%).

No wonder Vilna was known by Lithuanians as the "Jerusalem of Lithuania".

[Piotr Kapuscinski]

Thanks 4thskorpion. IMO those figures / percentages are too high, but I will check this.

BTW - here are the figures on total population and Jewish population of Warsaw from 1816 to 1941:

1564 - 25,000 (at that time there were 0 - zero - Jews in Warsaw)
1654 - 47,500 (another source gives this number under year 1624)
1780 - 70,000
1784 - 96,153 (1st exact census - previous figures are estimates)
1787 - 98,000
1792 - 120,000
1797 - 64,829 (2nd census) plus 10,806 soldiers of the garrison
1810 - 77,727 (3rd census)
1816 - 81,020 (including 15,579 believers of Judaism - 19,2%)
1817 - 88,362 (including 18,491 believers of Judaism - 20,9%)
1825 - 126,433 (including 28,044 believers of Judaism - 22,2%)
1829 - 139,654 (including 30,943 believers of Judaism - 22,2%)
1832 - 123,535 (including 31,384 believers of Judaism - 25,4%)
1856 - 156,562 (including 40,992 believers of Judaism - 26,2%)
1864 - 222,906 (including 72,776 believers of Judaism - 32,6%)
1877 - 308,548 (including 102,246 believers of Judaism - 33,1%)
1897 - 625,000 (including 210,500 believers of Judaism - 33,7%)
1900 - 683,692
1910 - 895,435 (including 308,488 believers of Judaism - 34,5%)
1914 - 885,000 (including 337,000 believers of Judaism - 38,1%)
1921 - 936,713 (including 310,322 believers of Judaism - 33,1%)
1931 - 1,171,898 (including 352,659 believers of Judaism - 30,1%)
1941 - 1,351,800 (including 411,000 believers of Judaism - 30,4%)

For comparison. As you can see % of Jews among the population was increasing, most of the time.

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BTW - differences in death causes among Christians & Jews of Warsaw in years ca. 1800 - 1805:

http://s29.postimg.org/t39i6kehj/Death_causes.png



Source: Cezary Kukło, "Demography of the Polish-Lithuanian Commonwealth", chapter 8 "Deaths".

[4thskorpion]

Thanks 4thskorpion. IMO those figures / percentages are too high, but I will check this.

BTW - here are the figures on total population and Jewish population of Warsaw from 1816 to 1941:

1564 - 25,000 (at that time there were 0 - zero - Jews in Warsaw)
1654 - 47,500 (another source gives this number under year 1624)
1780 - 70,000
1784 - 96,153 (1st exact census - previous figures are estimates)
1787 - 98,000
1792 - 120,000
1797 - 64,829 (2nd census) plus 10,806 soldiers of the garrison
1810 - 77,727 (3rd census)
1816 - 81,020 (including 15,579 believers of Judaism - 19,2%)
1817 - 88,362 (including 18,491 believers of Judaism - 20,9%)
1825 - 126,433 (including 28,044 believers of Judaism - 22,2%)
1829 - 139,654 (including 30,943 believers of Judaism - 22,2%)
1832 - 123,535 (including 31,384 believers of Judaism - 25,4%)
1856 - 156,562 (including 40,992 believers of Judaism - 26,2%)
1864 - 222,906 (including 72,776 believers of Judaism - 32,6%)
1877 - 308,548 (including 102,246 believers of Judaism - 33,1%)
1897 - 625,000 (including 210,500 believers of Judaism - 33,7%)
1900 - 683,692
1910 - 895,435 (including 308,488 believers of Judaism - 34,5%)
1914 - 885,000 (including 337,000 believers of Judaism - 38,1%)
1921 - 936,713 (including 310,322 believers of Judaism - 33,1%)
1931 - 1,171,898 (including 352,659 believers of Judaism - 30,1%)
1941 - 1,351,800 (including 411,000 believers of Judaism - 30,4%)

For comparison. As you can see % of Jews among the population was increasing, most of the time.

What happened in Warsaw in 1816 to cause the Jewish population of the city seemingly to jump from 0% to 19.2% or was it simply because religious faith was not recorded in any census data gathering prior to 1816?

[Piotr Kapuscinski]

No, you have misunderstood something - 0% of Jews was in 1564 (16th century), not immediately before 1816.

In the 1700s there was already a Jewish community in Warsaw, so it didn't jump from 0% in 1810 to 19% in 1816.

I just don't have exact data on Jewish population prior to 1816 at the moment, but surely such data also exists.

[4thskorpion]

No, you have misunderstood something - 0% of Jews was in 1564 (16th century), not immediately before 1816.

In the 1700s there was already a Jewish community in Warsaw, so it didn't jump from 0% in 1810 to 19% in 1816.

I just don't have exact data on Jewish population prior to 1816 at the moment, but surely such data also exists.

Ok. It would have been clearer to have added "believers of Judaism % not available." or similar to the dataset prior to 1816

Did you find the Jewish demographic data to on Vilna to confirm the information found at: http://www.yivoencyclopedia.org/article.aspx/Vilnius

[Piotr Kapuscinski]

Did you find the Jewish demographic data on Vilna

Yes I have found this data again:

Jewish population of Vilna / total population of Vilna / and Polish population of Vilna:

1897 - 61,847 Jews (40,0%) / total population 154,532 / number of Poles was falsified *
1910 - 75,500 Jews (41,3%) / total population 182,795 / including 97,800 Poles (53,5%)
1916 - 61,265 Jews (43,5%) / total population 140,890 / including 70,629 Poles (50,2%)
1917 - 57,516 Jews (41,5%) / total population 138,787 / including 74,466 Poles (53,7%)

* Many Roman Catholic Poles were counted as Great Russian-speakers or White Russian-speakers.

In this data above, figures for Jews are based on religion - i.e. believers of Judaism (and some of them were Polonised).

If counting Jews by national identity (Jewish nationality) or mother tongue (Yiddish + Hebrew), it was a smaller percent.

Now Polish data from the Inter-War period:

1923 - 55,437 Jews (33,1%) / total population 167,545 / including 100,830 Poles (60,2%)
1931 - 54,606 Jews (28,0%) / total population 195,071 / including 128,628 Poles (66,0%)

Figure of Jews from 1931 - 54,606 - is based on languages (Yiddish + Hebrew), religious composition of the city was:

Judaism believers - 55,006 (28,2%)
Roman Catholics - 125,999 (64,6%)
Orthodox people - 9,321 (4,8%)
Protestant people - 1,752 (0,9%)
Other Christians - 2,132 (1,1%)
Greek Catholics - 277 (0,1%)
Other & not stated - 584 (0,3%)

And also figures from censuses after the end of WW2 (1959 - after the deportation of most of Poles westward):

According to 1959 census (Soviet census):

Total population: 236,100 - including:

Lithuanians - 79,400 (34%)
Russians - 69,400 (29%)
Poles - 47,200 (20%)
Jews - 16,400 (7%)
Belarusians - 14,700 (6%)
Others - 9,000 (4%)

And also Lithuanian census from 2001:

Total population: 553,904 - including:

Lithuanians - 318,510 (57,5%)
Poles - 104,446 (18,9%)
Russians - 77,698 (14,0%)
Belarusians - 22,555 (4,1%)
Jews - 2,770 (0,5%)
Others - 27,925 (5,0%)

Compared to what you quoted:

The Jewish population of Vilna swelled to roughly 63,000 (41% of the total population) in 1897, to 76,000 in 1901 (46%), to 85,000 in 1903 (52%), and to perhaps as many as 100,000 in 1905 (51%).

Figures from 1901, 1903 and 1905 seem to be exaggerated.

But at least figure from 1897 is close to the truth.

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Percent and number of Lithuanians in the city of Wilno/Vilnius:

1897 census - 2,0% (3,131 Lithuanians out of 154,532)
1916 census - 2,6% (3,699 Lithuanians out of 140,890)
1917 census - 2,1% (2,909 Lithuanians out of 138,787)
1931 census - 0,8% (1,579 Lithuanians out of 195,021)
1959 census - 33,6% (79,400 Lithuanians out of 236,100)
2001 census - 57,5% (318,510 Lithuanians out of 553,904)

Vilnius became a majority-Lithuanian city around year 2000 AD.

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In 1897 Wilno was about as much Lithuanian, as Breslau was Polish in 1900 - let's compare:

Breslau 1900 census - 2,0% Polish (8,466 Polish-speakers out of 422,709 total population)
Wilno 1897 census - 2,0% Lithuanian (3,131 Lithuanian-speakers out of 154,532 total pop.)

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Overall ethnic trends from 1897 to 2011 (numbers from 1897 as reported in the census):

The decline of Russians from 1897 to 1910 was because those were Catholic Poles, counted as Russian-speakers in 1897:

[4thskorpion]

Did you find the Jewish demographic data on Vilna

Yes I have found this data again:

Thank you Peter. Do you know if the census results were ever manipulated or falsified by the Polish government(s) to support their territorial claims based on Polish majorities in the past? Was it mandatory for the population to participate in census data gathering?

In this data above, figures for Jews are based on religion - i.e. believers of Judaism (and some of them were Polonised).
If counting Jews by national identity (Jewish nationality) or mother tongue (Yiddish + Hebrew), it was a smaller percent.

Is the difference between whom you classify as "Jews based on religion" and "Jews by national identity" due to religious conversions to Judaism? Presumably through intermarriage?

[Piotr Kapuscinski]

Thank you Peter. Do you know if the census results were ever manipulated or falsified by the Polish government(s) to support their territorial claims based on Polish majorities in the past? Was it mandatory for the population to participate in census data gathering?

According to many historians there were manipulations in the census of 1931 in East Galicia, especially in Tarnopol and Stanisławów Voivodeships, in order to reduce (on paper) the number of Ukrainians/Rusyns and increase that of Poles. Other than that case, I don't know of any major falsifications. Later I will write more about those alleged falsifications in East Galicia in 1931, their methods and scale.

Researching pre-1918 Austrian data shows that large part of Polish-speaking and even Rusyn-speaking Greek Catholics in East Galicia indeed had Polish national identity. Apart from censuses - election results show that most of Jews and large part of Greek Catholicis in East Galicia voted for Polish lists (Polish parties), that was the case both under Austrian rules before WW1, and in independent Poland later.

Comparing 1931 data with 1921 data and with Austrian data, shows, that 1931 data was indeed manipulated, but the extent to which it was manipulated wasn't great. Number of Poles was overstated and that of Ukrainians understated by few percent each.

Is the difference between whom you classify as "Jews based on religion" and "Jews by national identity" due to religious conversions to Judaism? Presumably through intermarriage?

Jews based on religion are believers of Judaism. Jews by national identity are people who declared Jewish nationality in 1921 census.

Religious conversions to Judaism were generally not taking place, AFAIK. That was very rare in Europe. Last major conversions to Judaism took place under the Roman Republic, Hellenistic Kingdoms and in the Early Roman Empire. Perhaps also in the Khazar Khaganate later on.

Modern genetic research - such as the presentation by J. Xue and S. Carmi "The Time and Place of European Gene Flow Into Ashkenazi Jews" from the Biology of Genomes 2015 conference - suggests that Ashkenazi Jews are in ~50% of Middle Eastern ancestry ("original", Ancient Jewish ancestry), in ~35% of South European ancestry (admixture from individuals who converted to Judaism in Hellenistic and Roman times, ca. 2000 years ago), in ~12% East European (mostly Medieval admixture, perhaps Slavic and Khazar conversions) and in ~3% West European.

As for intermarriage (mostly occuring between Poles and non-religious Jews or Jews who converted to Christianity) - intermarriage could play some role, indeed. But there were also many unmixed Jewish couples, who still identified as nationally Polish, rather than Jewish.

This data can be found for example here: https://books.google.pl/books?id=5_OXOw ... &q&f=false

Jews from former Austrian West Galicia (Cracow) were most Polonised, followed by Jews from East Galicia (as I wrote above):

Jewish Poles.png (51.81 KiB) Viewed 4062 times

Jewish Poles 2.png (101.06 KiB) Viewed 4062 times