Complex sentence: Despite his status as a former Mississippi senator, Walker supported the Union cause during the American Civil War and in 1863 and 1864, as financial agent of the United States, did much to create confidence in Europe in the financial resources of the United States.
Split into simpler sentences: Despite his status as a former Mississippi senator, Walker supported the Union cause during the American Civil War. In n 1863 and 1864, as financial agent of the United States in Europe, Walker did much to create confidence in Europe in the financial resources of the United States.