This paper deals with the way Jews took part in the wars of the Revolutionary and Napoleonic times. I focus on the intellectual debates which took place a few years before the Revolution, a time when thinkers such as Döhm, Moses Mendelssohn, Abbé Grégoire or Zalkind Hourwitz produced their major works, tackling the question of the ban to bear arms on Shabbat and the way this could prevent the Jews from being soldiers, and therefore citizens. I will show that Napoléon was inspired by such thinkers when he conceived his famous reforms, from 1806 onwards, and underline the birth of a rhetoric glorifying the Jews as Jewish warriors, produced by the Consistoires and influencing personal narratives, for example the memoirs of Jakob Meyer. However, when the Grande Armée arrived in Poland in 1806-1807, the participation of the Jews of Poland was much different, since they played a key role as military auxiliaries, carriers, food-suppliers, interpreters and guides, all forms of help which I choose to categorize under the concept of War Jews, a term reminiscent of Court Jews. This participation is evidenced in many memoirs, military archives, as well as in some caricatures and literary productions, which qualify the emancipatory paradigm. Finally, the rabbinical position over the question of the presence of the Jews in the army is interesting, from the opposition of most of Hasidim and Misnagdim, to the enthusiastic call to a general war, led by Menahem Mendel Rymanower, as Martin Buber summarized in his Gog und Magog.