The Union troops reinforced their positions at Gettysburg By building fortifications.

Following the initial skirmishes on the first day, Union forces took advantage of elevated positions like Cemetery Ridge and Little Round Top to create formidable defensive lines. They built earthworks, barricades, and breastworks to strengthen their defenses against Confederate assaults. This strategic preparation enabled the effective placement of Union artillery, optimizing their firepower. The strong fortifications were vital in enduring Confederate attacks on July 2 and 3, ultimately aiding the Union's victory.