Complex sentence: During the early part of the Civil War, Higginson was a captain in the 51st Massachusetts Infantry from November 1862 to October 1864, when he was retired because of a wound received in the preceding August.
Split into simpler sentences: During the early part of the Civil War, Higginson was a captain in the 51st Massachusetts Infantry. From November 1862 to October 1864, when he was retired because of a wound received in the preceding August.