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