The first two elements of the Tosafist enterprise—i.e., (1) independent analysis and (2) integration of earlier teachings—were the focus of Talmud study for both French and German Tosafists in the late twelfth and early thirteenth centuries. However, it was specifically the French works that ultimately formed the backbone of extant Tosafist commentaries, especially those that are printed today in the margins of the Talmud.
The dominance of the French works is largely due to the emergence of R. Isaac of Dampierre (Ri, d. 1189) and the establishment of his Tosafist academy in Dampierre. Ri was a nephew of R. Tam and his greatest rival for prominence in Tosafist history. Ri’s prolific lectures educated scores of Tosafists, and his students spread the Tosafist approach to all corners of Europe, including France, Germany, Italy, Provence, and the Slavic lands. Ri was a towering innovator and blessed with a creativity that allowed him to formulate many original contributions as an independent Tosafist. However, Ri was also the driving force and epitome of the second element in the Tosafist enterprise: integration
Aryeh Leibowitz, “The Emergence and Development of Tosafot on the Talmud”, Hakirah 15 (Summer 2013), 154-155.