The battle of Antietam, fought over an area of 12 square miles, consisted of the three basic phases—morning, midday, and afternoon—shown on the maps at right. During the morning phase, three piecemeal Union attacks drove back Jackson’s line, but did not break it. The midday phase saw two Union divisions break D. H. Hill’s line in the sunken road, but McClellan’s failure to follow it up lost him the advantage that had been gained. In the afternoon phase, Burnside’s slow pincer movement beyond the lower bridge was broken by A. P. Hill’s timely arrival.

Morning Phase

Midday Phase

Afternoon Phase

Transcriber’s Notes