Complex sentence: From October 1934 to 1935 he served in the Reichswehr, but he decided a greater opportunity to be a professional soldier was to be found in the SS, which he joined in April 1936.
Split into simpler sentences: From October 1934 to 1935 he served in the Reichswehr. In his opinion a greater opportunity to be a professional soldier was to be found in the SS, which he joined in April 1936.