Complex sentence: He thus sought out civilians and officers who opposed Hitler, such as Erwin von Witzleben, who dissuaded Tresckow from resigning from the Army arguing that they would be needed when the day of reckoning came.
Split into simpler sentences: He thus sought out civilians and officers who opposed Hitler, such as Erwin von Witzleben. Witzleben dissuaded Tresckow from resigning from the Army arguing that they would be needed when the day of reckoning came.