In early October 1944, the 9th Armored Division landed in France and was immediately deployed eastward to advance into Luxembourg. When the Germans began their Ardennes offensive on December 16, 1944, the "Phantom" division was deployed just north of Diekirch, a few miles east southeast of Bastogne, Belgium. As the Germans attacked US positions near St. Vith on the northern sector of the front, part of the 9th was transferred to assist in defending the city. The units of the 9th Armored Division engaged in fierce combat that bought the US commanders time to organize the defense of Bastogne in which became known as the Battle of the Bulge. By the time they withdrew to the eastern outskirts of the town, the units of the 9th had withstood repeated attacks on the roads leading to Bastogne.
On March 7, 1945, the unit captured the Ludendorff Bridge over the Rhine River at the city of Remagen. The 9th continued its drive into central Germany and by war's end had advanced into Czechoslovakia.
On May 8, 1945, troops of the 9th, along with comrades from the 1st Infantry Division, liberated Zwodau and Falkenau an der Eger, both subcamps of the Flossenbürg concentration camp. Both camps were located on the territory of what today is the Czech Republic. SS entrepreneurs had established Zwodau in 1944 for the production of air force equipment and, by March 1945, it housed some 1,200 female prisoners. Falkenau housed 60 prisoners.
At the time of its liberation, the camp in Zwodau held some 900–1,000 starving women prisoners. The army divisions procured food from the neighboring areas and provided badly needed medical attention to the survivors.
The 9th Armored Division was recognized as a liberating unit by the US Army's Center of Military History and the United States Holocaust Memorial Museum in 1993.
Casualty figures for the 9th Armored Division, European theater of operations :
- Total battle casualties: 3,845
- Total deaths in battle: 728
Although no nickname for the 9th was in common usage throughout the war, "Phantom" division was sometimes used in 1945. It originated during the Battle of the Bulge, when the 9th Armored Division seemed, like a phantom, to be everywhere along the front.