Complex sentence: The son of an aristocratic family, Retzow was educated at the cavalry academy in Brandenburg and entered the regiment "von Schlabrendorff" at the age of 17 as a cadet.
Split into simpler sentences: The son of an aristocratic family, Retzow was educated at the cavalry academy in Brandenburg. He entered the regiment "von Schlabrendorff" at the age of 17 as a cadet.