Complex sentence: In 1939, he demanded mass sterilization in the United States; two years later he shifted his focus to the forced, mass-sterilization, through castration, of all German men under 65 and the sterilization of most German women under 45.
Split into simpler sentences: In 1939, he demanded mass sterilization in the United States. Two years later he shifted his focus to the forced, mass-sterilization, through castration, of all German men under 65 and the sterilization of most German women under 45.