Complex sentence: Marius had no troops with which to conduct the war in Africa as the eligible citizenry from whom he could recruit an army was severely depleted due to previous military disasters and the expansion of the latifundia at the expense of small landowners.
Split into simpler sentences: Marius had no troops with which to conduct the war in Africa. The eligible citizenry from whom he could recruit an army was severely depleted due previous military disasters and the expansion of latifundia at the expense of small landowners.