Complex sentence: For posterity Holst is known both for his work with the Norwegian resistance and for the circumstances surrounding his death in Stockholm, at the time so much talked of that the Milorg leadership issued a statement in the Norwegian newspaper "Aftenposten" in July 1945.
Split into simpler sentences: For posterity Holst is known both for his work with the Norwegian resistance and for the circumstances surrounding his death in Stockholm in 1945. Holst's demise was so much talked of at the time that the Milorg leadership issued a statement in the Norwegian newspaper "Aftenposten" in July 1945.