noun, masculine/pjɔ.nje/plural: pionniers
pioneer, soldier employed to form roads, dig trenches, and make bridges, as an army advances; pioneer, one who goes before, as into the wilderness, preparing the way for others to follow; precursor; pioneer, child of 10–16 years in the former Soviet Union, in the second of the three stages in becoming a member of the Communist Party
“Toute la tranchée connaît à présent la nouvelle (...). Il paraît que les pionniers vont venir cette nuit, pour préparer les escaliers d'attaque. On doit installer des petits canons de 37 et des lance-bombes.”
From Old French peonier (“infantryman”), from peon (“footman”) (modern French pion), from Latin pedōnem.