Complex sentence: In 1940, while in his adoptive country under German occupation, he was captured and deported to the Mauthausen concentration camp, as many other Republican exiled, from where he would not leave until the end of World War II, in 1945.
Split into simpler sentences: In 1940, while his adoptive country was under German occupation, he was captured and deported to the Mauthausen concentration camp, as were many other Republican exiles. He would not leave until the end of World War II, in 1945.