Complex sentence: After World War I, AC B became responsible solely for traffic and lost property, with his other former duties divided between ACs A and L. AC L was responsible for L (Legal) Department until its reorganisation in 1931.
Split into simpler sentences: After World War I, Assistant Commissioner "B" became responsible solely for traffic and lost property, with his other former duties divided between Assistant Commissioners "A" and "L". Assistant Commissioner "L" was responsible for "L" (Legal) Department until its reorganisation in 1931.