He was a staunch defender of Captain Alfred Dreyfus, whom he considered an innocent man. The artist's suspicions were substantiated after one of Dreyfus's accusers broke down under interrogation. Hubert-Joseph Henry confessed that the damning documents were actually forged. After Henry slit his throat in prison, Hermann-Paul produced a cartoon in which two people stand over the fresh grave of Major Henry. One says to the other, "This one, at least, won't give us any trouble." "Avec celui-là au moins on est tranquille."