Complex sentence: They moved to Zagreb when Brendel was six, and later to Graz, where they lived during World War II, towards the end of which the 14 year old Brendel was sent to Yugoslavia to dig trenches.
Split into simpler sentences: They moved to Zagreb when Brendel was six, and later to Graz. They lived there during World War II, towards the end of which the 14 year old Brendel was sent to Yugoslavia to dig trenches.