Complex sentence: He was appointed as chief on 17 November 1934 and held that position until 23 April 1945; though largely disempowered from 1942 onwards in favour of Martin Bormann.
Split into simpler sentences: He was appointed as chief on 17 November 1934 and held that position until 23 April 1945. However, he was largely disempowered from 1942 onwards in favour of Martin Bormann.