 Nyora kupfuurira kweiyi ndima - Kubva muna 1805 zvichienda mberi, Saint-Hilaire aizoramba achishanda mu Grande Armée, achibata mauto akasiyana-siyana. Muna 1805, akatungamira chikamu muMarchal Jean-de-Dieu Soults IV Corps panguva yeHondo yeChitatu Chibvumirano uye paHondo yeAusterlitz, akatungamira kurwisa kwakasarudzika paPratzen plateau, achigamuchira ronda rakakomba pakutanga kwekurwisa asi zvakadaro achichengetedza kutungamira kwake kwehondo yese. Pakati pa1806 na1807, akarwa zvine mbiri paJena, Eylau neHeilsberg. Akaitwa Count of the Empire muna 1808 uye akagamuchira kutungamira kwemauto muuto reGermany, raizomhanya naro kumaodzanyemba kweGermany neAustria. Musi waApril 22, 1809, Saint-Hilaire akazviratidza pamberi paNapoleon paHondo yeEckmühl. 