I have an earlier answer on the rise of the Ukrainian movement in Eastern Galicia which might interest you.

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The local Ukrainian-speaking inhabitants living in the eastern half of Galicia (which, for simplicity's sake, I will refer to as "Ruthenians" from now on) had their pick of five national ideas, among them Galician, Polish, Rusyn, Russian, and Ukrainian. In the end, as you already know, most of the Ruthenians in eastern Galicia adopted a Ukrainian identity, transforming the region into a bastion of Ukrainian nationalism. The other four competing national projects failed to win the loyalty of Ruthenians because they did not have the Ukrainian movement’s popular appeal, political support, and organizational strength.

The Galician project was the first contestant to fail in eastern Galicia because it made no effort to attract Ruthenians. During the reign of Joseph II, Austrian administrators attempted to encourage a Galician political identity, based on one’s status as a subject of the Habsburg monarch, among the Polish szlachta in Galicia (Wolff, “Inventing Galicia” 822-823). This project was fundamentally meant to re-orient the newly conquered szlachta away from the rump Polish-Lithuanian Commonwealth and toward Vienna. While the Habsburg Emperor would not have minded Ruthenians adopting a Galician identity, they were never the target audience of this proposed nation, and so they never joined. The Galician national project largely lost steam after the final partition of Poland in 1795, when Joseph’s successor Leopold II judged there to no longer be any other competition for the loyalty of the szlachta (Wolff, “Inventing Galicia” 837). Without state support, there was even less incentive for Ruthenians to adopt a Galician nationality, so Joseph’s project gave way to other national movements courting the loyalty of Ruthenians. With the apparent absence of any competing national identity, the Polish movement seemed poised to absorb the Ruthenian population, but this proved to be an illusion.

Polish national activists failed to turn Galician Ruthenians into loyal Poles due to social and political hurdles. Now, in Eastern Galicia, religious and ethnic differences heavily aligned. In general, Poles were Roman Catholic, while Ruthenians were Greek Catholic. While both the Roman Catholics and Greek Catholics recognize the authority of the Pope of Rome, there are numerous differences between the two denominations, one in particular revolving around the ordination of married men. In contrast to Roman Catholic practice, the Greek Catholic Churches (e.g., the Ukrainian Greek Catholic Church) allowed the ordination of married men to the priesthood. This practice resulted in Galician Ruthenian society developing a class of priestly families, each supplying generations of priests in a particular parish or region. While centuries of Polish dominance had led to a hybrid Ruthenian-Polish identity (summarized by the Latin phrase gente Ruthenus, natione Polonus) among the Ruthenian ecclesiastical elite, their priestly profession obstructed Ruthenian priests from fully adopting a Polish nationality. To become "true" Poles, Ruthenians had to switch from Greek Catholicism to Roman Catholicism, a choice which married Ruthenian Greek Catholic priests simply could not make without abandoning their clerical careers (Himka, “The Construction of Nationality in Galician Rus’” 117-119). As for the Ruthenian peasant majority, they perceived Polish identity as fundamentally linked with the landlord class. Not only did this mean that the average Ruthenian peasant considered it impossible for them to become a Pole, it also meant the common Ruthenian perceived the interests of Poles as fundamentally different from their own (Himka, “The Construction of Nationality in Galician Rus’” 123-124). This ravine obstructing the Polonization of Ruthenians only grew thanks to the actions of Austrian administrators.

[Continued into part II]