Complex sentence: Július Tomin (1915--2003), a high school teacher and well-known author from Czechoslovakia, was persecuted during the Soviet occupation for promoting Interlingua as a second language.
Split into simpler sentences: Július Tomin (1915--2003) was a high school teacher and well-known author from Czechoslovakia. It was persecuted during the Soviet occupation for promoting Interlingua as a second language.