When Rav Yiztḥak Luria, zt”l, also known as the Holy Ari, davvened in Eretz Yisroel he brought about a series of liturgical innovations witnessed in later siddurim. His particular nusaḥ bridged minhag Ashkenaz and minhag Sefarad (the customs of the Rheinland Jews and the customs of the Jews of the Iberian Peninsula) with the teachings of his school of Kabbalists. When two centuries later, the Ḥassidic movement blossomed in Eastern Europe, it found purchase in Lithuania among a mystical school centered around Rav Schneur Zalman of Lyady, the Alter Rebbe and founder of the ḤaBaD movement within Ḥassidism. The Alter Rebbe compiled his own siddur, the Siddur Torah Ohr, “according to the tradition of the Ari.” . . .