During the American Civil War, Le Sére served in the Confederate States Army, first as major of the 10th Louisiana Regiment, and later as chief quartermaster of the Trans-Mississippi Department.
dˈʊɹɹɪŋ ðɪ ɐmˈɛɹɪkən sˈɪvəl wˈɔːɹ, lə sˈeɪɹə sˈɜːvd ɪnðə kənfˈɛdɚɹət stˈeɪts ˈɑːɹmi, fˈɜːst æz mˈeɪdʒɚɹ ʌvðə tˈɛnθ luːˌiːzɪˈænɚ ɹˈɛdʒɪmənt, ænd lˈeɪɾɚɹ æz tʃˈiːf kwˈɔːɹɾɚmˌæstɚɹ ʌvðə tɹˈænzmˌɪsɪsˈɪpi dᵻpˈɑːɹtmənt.