Complex sentence: Wounded in the Second Battle of Fredricksburg in spring 1863 Crawford was sent to Philadelphia to convalesce; during his recovery, he attended the first officer training school designed to train white officers assigned to command U.S. Colored Troops.
Split into simpler sentences: Wounded in the Second Battle of Fredricksburg in spring 1863, Crawford was sent to Philadelphia to convalesce. During his recovery, he attended the first officer training school designed to train white officers assigned to command U.S. Colored Troops.