Complex sentence: Dumont would serve under Riel as adjutant general in the provisional Métis government declared in Saskatchewan in 1885, and commanded the Métis forces in the North-West Rebellion.
Split into simpler sentences: Dumont would serve under Riel as adjutant general in the provisional Métis government declared in Saskatchewan in 1885. Dumont then commanded the Métis forces in the North-West Rebellion.