The Union forces responded to Confederate advances on the first day by They retreated.

At first, Union troops, especially from the Eleventh Corps, entered the battle but were met with fierce Confederate attacks, particularly on their flanks. As the circumstances worsened, Union forces were forced to retreat through Gettysburg to regroup on elevated terrain like Cemetery Hill. This strategic withdrawal laid the groundwork for the intense fighting that followed, as Union leaders sought to fortify their defenses against impending Confederate assaults.