Complex sentence: During World War II, from 1943, Loesser served for the US Army where he worked in the Japanese intlligence department, it was during this period that he mastered the Japanese language and after the war ended he gave recitals with lectures in Tokyo.
Split into simpler sentences: During World War II, from 1943, Loesser served for the US Army where he worked in the Japanese intlligence department. It was during this period that he mastered the Japanese language and after the war ended he gave recitals with lectures in Tokyo.