Complex sentence: After France was defeated in the spring of 1940, Alsace and Moselle never were officially annexed by Germany, however they were administered from Berlin until German defeat in 1945, when they were returned to France.
Split into simpler sentences: After France was defeated in the spring of 1940, Alsace and Moselle were not officially annexed by Germany. However they were administered from Berlin until German defeat in 1945, when they were returned to France.