 He was present at the Battle of Antietam, where his brigade saved the flank of the Union Army late in the day.During the Vicksburg campaign, Ewing accidentally came across personal correspondence from Confederate President Jefferson F. Davis to former President Franklin Pierce which eventually ruined the reputation of the latter.Ewing was also present in Kentucky during Major General Stephen G. Burbridge's "reign of terror", where he worked to oppose Burbridge's harsh policies against civilians, but was hampered by debilitating rheumatism.