Complex sentence: Kurt Diebner (13 May, 1905--13 July, 1964) was a German physicist who, during World War II was a member of the German nuclear energy project in Nazi Germany which may have been trying to develop a nuclear weapon from enriched uranium.
Split into simpler sentences: Kurt Diebner (13 May, 1905--13 July, 1964) was a German physicist. During World War II, he was a member of the German nuclear energy project in Nazi Germany; the project which may have been trying to develop a nuclear weapon from enriched uranium.