Complex sentence: In punishment for dissenting remarks, Severloh was forced to perform physical exertions which left him with permanent health problems and a six-month convalescence in a military hospital, until June 1943.
Split into simpler sentences: In punishment for dissenting remarks, Severloh was forced to perform physical exertions which left him with permanent health problems. The immediate consequence was a six month convalescence in a military hospital, which lasted until June 1943.