Complex sentence: Hebert left the post in 1951 after four years of service, when at the age of fifty-five, he sustained a life-altering stroke, which required caregivers for the remainder of his life.
Split into simpler sentences: Hebert left the post in 1951 after four years of service. At the age of fifty-five, he sustained a life-altering stroke, which required caregivers for the remainder of his life.