The 9th Infantry Division rested and refitted for the major breakthrough offensive, codenamed COBRA.
COBRA envisioned a massive “carpet bombing” followed by three infantry divisions attacking to punch a hole in enemy lines, and then two armored divisions and a motorized infantry division exploiting through the hole thus made.

As the gap widened and resistance crumpled, further forces would pour through or follow up in pursuit.
The three infantry divisions to make the initial attack were, from right to left, the 9th, 4th and 30th.
COBRA was set for 21 July, but was postponed to 22, 24 and then 25 July because of weather.
On the morning of 25 July more than 2,400 Allied planes dropped more than 4,000 tons of bombs within six-square-mile sector of the German front west of Saint-Lô.

The 9th Infantry Division attacked at 1100, and by nightfall forced its way across the Périers - Saint-Lô Highway.
The bombing and infantry attacks totally disrupted the defenders along 7,000 yards of the enemy front.