Complex sentence: Ouimet raised three hundred men and led his regiment as its Lieutenant-Colonel and was put under the command of Thomas Bland Strange who rejected Ouimet's proposal to negotiate safe passage for Riel.
Split into simpler sentences: Ouimet raised three hundred men, and led his regiment as its Lieutenant-Colonel. He was put under the command of Thomas Bland Strange who rejected Ouimet's proposal to negotiate safe passage for Riel.