An advantage of davening in a minyan in a local yeshiva is that you never know what seforim might turn up or what you might find in them.
This past Shabbat I found a copy of Mateh Levi (it's a bit different from the standard printed volume; much fewer responsa). This book, which is mainly about writing Gittin but also contains responsa on all sorts of issues, was written by R. Dr. Mordechai (Markus) Halevi Horovitz, a Hungarian rav who eventually became the rabbi of general (i.e., non-secessionist) Orthodox community in Frankfurt (or Vrankvurt, as it is spelled in this book). That is, he was a rival and critic of RSR Hirsch.
As you can see from the stamp, this particular volume, printed in 1891, belonged to the library of the Berlin Jewish community. There are actually stamps indicating that it was checked out of that library several times in the early 1920s. It eventually found its way to the yeshiva high school in Modiin, where I peruse it on Shabbat.
The first responsum begins with a question from R. Asher Grossberg of Eszlar.
R. Asher begins the query by reintroducing himself, reminding R. Horowitz that they studied together in Ujhely (a major Hungarian yeshiva) and met again at the famed Jewish Congress that took place in the winter of 1868-9. He also mentions that R. Horovitz was then working on a treatise to prove that Hungarian Jews are descendants of the Khazars.Dual Monarchy was established in 1867, Hungarians became a minority within their own kingdom. To help alleviate that, they extended full civil rights to the Jews, on condition that the Jews would declare "Magyar" (=Hungarian) as their nationality. The Jews, by and large, saw the opportunity and went along with it. Some, like R. Akiva Yosef Schlesinger, were strongly opposed, maintaining that this is a betrayal of Jewish nationhood (he was a Haredi and a Zionist, by any definition of either). Eventually, it became popular to claim that Hungarian Jews were descendants of the Khazars who migrated westward along with the other Hungarian tribes in the Middle Ages - that is, that Hungarian Jews are indeed as Hungarian as any Hungarian.
It is surprising to me that such theories were being propounded by respected rabbanim so soon after the process of Magyarization began.
To dispel doubt: I do not believe that Hungarian Jews, or any other Jews, are the descendants of the Khazars, nor do I believe that there was ever a mass conversion of Khazars to Judaism.