Original sentence: He notes that period from 1863 to 1881 was witnessing the increase of anti-Semitism in Poland, with disillusionment among Poles with the idea of assimilation of the Jews was growing, and hence there was less need for the Russian authorities to orchestrate a pogrom, which might have been indeed spontaneous
Edited sentence: He notes that period from 1863 to 1881 was witnessing the increase of anti-Semitism in Poland, with disillusionment among Poles with the idea of assimilation of the Jews was growing, and hence there was less need for the Russian authorities to orchestrate a pogrom, which might have been spontaneous