Complex sentence: In August 1865, Banks was mustered out of the service by President Andrew Johnson, and from 1865 to 1873, he was again a representative in Congress, serving as chairman of the Foreign Affairs Committee and sometimes as chair of the Republican caucus.
Split into simpler sentences: In August 1865, Banks was mustered out of the service by President Andrew Johnson. He was elected as a representative to Congress, serving from 1865 to 1873, when he held the positions of chairman of the Foreign Affairs Committee and sometimes as chair of the Republican caucus.