The first elements of the 3rd Armored in France saw combat on 29 June, with the division as a whole beginning combat operations on 9 July 1944. During this time, it was under the command of VII Corps and XVIII Airborne Corps for some time, and assigned to the First Army and the 12th Army Group for the duration of its career.
The division "spearheaded" the US First Army through Normandy, taking part in a number of engagements, notably including the Battle of Saint Lô, where it suffered significant casualties. After facing heavy fighting in the hedgerows, and developing methods to overcome the vast thickets of brush and earth that constrained its mobility, the unit broke out at Marigny, alongside the 1st Infantry Division, and swung south to Mayenne.
Ordered to help close the Falaise Gap and Argentan pocket which contained the German Seventh Army, the division finished the job near Putanges by 18 August. Six days later the outfit had sped through Courville and Chartres and was located at the banks of the Seine River. On the night of 25 August 1944 the crossing of the Seine by the division started; once over, the 3rd slugged its way across France, reaching Belgium on 2 September 1944.
Liberated in the path of the division were Meaux, Seissons, Laon, Marle, Mons, Charleroi, Namur and Liege. It was at Mons that the division cut off 40,000 Wehrmacht troops and captured 8,000 prisoners. "Then the division began the first invasion of Germany since the days of Napoleon" is a claim often repeated and derives from 1947 U.S. Army literature that ignored earlier acts such as the 5th Armored Division's reconnaissance into Germany on 11 September 1944, French troops entering the Saarland in September 1939 during the Saar Offensive, and the entry into Germany by imperial Russian troops in 1914.
On 10 September 1944 the Spearhead Division fired what it claimed was the first American field artillery shell of the war onto German soil. Two days later it passed the German border and soon breached the Siegfried Line, taking part in the Battle of Hurtgen Forest.
The 3rd Armored Division continued fighting during the Battle of Bulge, far north of the deepest German penetration. Countering German attacks, it severed an important highway leading to St Vith. By late January 1945, the German offensive had been checked, and the division began pushing its way into Germany. Advancing at a little better than half a mile a day against stiff resistance, the 3rd captured ten towns in January 1945, took 2,149 prisoners and destroyed 61 armored vehicles.
The 3rd Armored Division had 231 days of combat in World War II, with a total of 2,540 killed, 7,331 wounded, 95 missing, and 139 captured. Total battle and non-battle casualties came to 16,122.
The 3rd Armored Division lost more tanks in combat than any other U.S. division. Combat Command A lost more tanks than any other unit in the 3rd Armored Division.