Marcus Jastrow spent 40 years of his life writing an enormous dictionary that has an English translation for every single word in the Talmud.
He was ordained as a rabbi at a young age and left his native Prussia to go work in Poland. In this era, in Poland, Jews spoke Yiddish, (Christian) Poles spoke Polish, and the ruling Russians spoke Russian. (It was in this linguistically divided environment that Zamenhof invented Esperanto).
Jastrow learned Polish and gave a sermon in Polish about the Russians murdering Polish activists. It was so popular that the next day he gave it again to note takers who circumvented the ban on Jews publishing by hand-writing 1000 copies of it and distributing it on the streets.