Arriving 15 December 1943, the 4th was encamped in the town of Singleton, West Sussex near the English southern coast. Immediately upon arrival the 4th Cavalry Regiment was redesignated and reorganized as the 4th Cavalry Group, Mechanized. The 1st Squadron was reorganized and redesignated as the 4th Cavalry Reconnaissance Squadron, Mechanized and the 2nd Squadron was reorganized and redesignated as the 24th Cavalry Reconnaissance Squadron, Mechanized.

In preparation for the Normandy invasion the 4th Cavalry was assigned a critical role in the amphibious assault of the VII Corps onto Utah Beach. Aerial reconnaissance showed German fortifications on the St. Marcouf Islands 6000 yards off of Utah Beach. These fortifications could pose a serious threat to the Utah Beach landings. The 4th Cavalry was assigned the mission of neutralizing them prior to the landing. The 4th also had the mission of getting two troops ashore on D-Day to link up with the 82nd and 101st Airborne Divisions to give them armor support.

At 0430 Hours 06 June 1944, elements of "A" Troop, 4th Squadron and "B" Troop, 24th Squadron landed on the St. Marcoufs. Corporal Harvey S. Olsen and Private Thomas C. Killeran of "A" Troop, with Sergeant John S. Zanders and Corporal Melvin F. Kinzie of "B" Troop, each armed only with a knife, swam ashore to mark the beaches for the landing crafts. They became the first seaborne American soldiers to land on French soil on D-Day.

As the troops dashed from their landing craft they were met with silence. The Germans had evacuated the islands but they did leave them heavily mined. Meanwhile one platoon of "B" Troop, 4th Squadron got ashore at Utah Beach and liked up with the 82nd Airborne. On 07 June the platoon surprised a German column and in a mechanized cavalry charge hit the column routing it with a loss of some 200 casualties. Heavy seas prevented "C" Troop from linking up with the 101st until 08 June.

As the American forces swung into the Cherbourg peninsula the 4th Cavalry Group's two squadrons performed flank protection for the 4th and 9th Infantry Divisions. In the Cape de la Hague area the 4th Squadron fighting dismounted seized all of its objectives in five days of bloody fighting capturing over 600 prisoners. Both the 4th and 24th Cavalry Squadrons were awarded the French Croix De Guerre with Silver Star for their gallantry on the Cherbourg peninsula.

After breaking out of the Normandy hedgerows at St Lo in July 1944, the VII Corps attacked east toward Paris. In the dash across France the 4th Cavalry Group assumed traditional cavalry missions of flank screening and protection of lines of communications for the VII Corps. Paris was liberated on 24 August as the 4th Cavalry Group by-passed the city crossing the Seine River on 25 August and the Marne River on 31 August.

As the VII Corps prepared to enter Belgium it attached the 759th Light Tank Battalion to the 4th Cavalry Group to support the Group's protection of the VII Corp's right flank and rear. Also, shortly thereafter, the 635th Tank Destroyer Battalion (Self-Propelled) and the 87th Armored Field Artillery Battalion were attached. Along with the two reconnaissance squadrons the attachments gave the 4th Cavalry the strength of a light armored brigade as it crossed into Germany on 14 September and penetrated the Siegfried Line. By late November the 4th Cavalry Group had moved with the VII Corps into the Hurtgen Forest meeting stiff German resistance.

On 16 December 1944 the German Army launched its surprise attack against lightly-held Allied positions in the Ardennes. While the attention of the world was focused on the early stages of what would become known as the Battle of the Bulge, some of the fiercest fighting of the war erupted to the north on the 19th, 20th and 21st of December in the VII Corps sector on the edges of the Hurtgen Forest along the approaches to the Roer River. It was here that the 4th Cavalry Group was given the mission to seize the heavily fortified town of Bogheim and the high ground to its southeast.

On 19 December, under a ground fog, two troops of the 4th Squadron got into the town undetected and engaged the Germans. Two other troops coming up in support were caught in the open, as the fog lifted and took heavy casualties. The two troops already in the town successfully drove out the Germans by the afternoon. But, not without losses, all four troop commanders had either been killed or wounded and over one fourth of the enlisted personnel had also become casualties. The next morning the 4th Squadron charged dismounted across two hundred yards of open terrain to seize the high ground overlooking the town. In the battle for Bogheim, the 4th Squadron destroyed two battle groups of the 947th German Infantry and a company of the 6th Parachute Regiment. For its magnificent bravery at Bogheim the 4th Cavalry Reconnaissance Squadron was awarded a Presidential Unit Citation.

As the German Ardennes offensive pushed westward the VII Corps was shifted south into Belgium to blunt its advance. By 23 December, the 4th Cavalry Group was in contact with advancing German forces. On 24 December the 4th Cavalry Group was attached to the 2nd Armored Division and ordered to defend the key road junction of Humain to prevent the Germans from driving a wedge between the 2nd Armored and the 84th Infantry Divisions. The 4th Squadron was screening to the west between Combat Commands "A" and "B" of the 2nd Armored Division, leaving the 24th Squadron to defend Humain. By midnight "A" Troop, 24th Squadron had taken Humain. But by early Christmas morning "A" Troop was forced out of the town by a strong German panzer attack. Attempts to retake the town by the lightly armored 24th Squadron made little progress against the heavy German armor. Nevertheless by 26 December the 2nd Armored Division along with the 24th Squadron had repelled the German attack in the Humain sector and significantly contributed to ending the German attempts to continue their westward advance across the Meuse River toward Antwerp.

After retaking the territory lost to the Germans during the Battle of the Bulge Allied forces resumed their advance into Germany. The 4th Cavalry Group conducted screening missions for the VII Corps in the advance to the Roer River in February and the closing of the Ruhr Pocket. On 07 April as the war drew to a close, the last major operation assigned to the 4th Cavalry Group (Reinforced) was to eliminate the 85,000 strong German force holding out in the Harz Mountains. By 21 April the 4th Cavalry Group had accomplished its mission. From there the 4th Cavalry Group went on to conduct mopping-up operations along the Elbe River and had reached the city of Leipzig when hostilities ended on 8 May 1945.

"E" Trp, 24th Constabulary Formation

For occupation duties in Germany and Austria the Army organized the US Constabulary. The 4th Cavalry Group was redesignated the 4th Constabulary Regiment with the 4th and 24th Constabulary Squadrons. The Headquarters of the 4th Constabulary Regiment was stationed at Camp McCauley in Hoersching near Linz, Austria. The 4th Constabulary Squadron was stationed at Wells and the 24th Constabulary Squadron at Ebelsburg. Troops of the regiment were posted at seven other towns throughout the American occupation zone of Austria conducting law and order and security missions. On 01 May 1949, the 4th Constabulary Regiment was inactivated. Also on 01 May, the 24th Constabulary Squadron was transferred to Bad Herzfeld, West Germany, where it performed border surveillance until its inactivation on 15 December 1952.

On 21 April 1953, the 24th was redesignated in an inactive status as the 524th Reconnaissance Battalion. On 01 April 1949, the 4th Constabulary Squadron was reorganized and redesignated as the 4th Reconnaissance Battalion and then subsequently on 01 December 1951, as the 4th Armored Cavalry Reconnaissance Battalion and remained at Camp McCauley until its inactivation on 01 July 1955. To perpetuate some small remnant of the 4th Cavalry on active duty, Headquarters and Headquarters Company, 4th Armored Cavalry Reconnaissance Battalion was reorganized and redesignated as Headquarters and Headquarters Company, 4th Armor Group and activated at Gibbs Barracks in Frankfurt, West Germany, assigned to the 7th Army and placed under the operational control of the V Corps.

There were three separate tank battalions and two armored infantry battalions attached to the 4th Armor Group. These units were stationed at various locations within the Northern Sector Command of the 7th Army. On 01 April 1963, Headquarters and Headquarters Company, 4th Armor Group was inactivated at Frankfurt and redesignated in an inactive status as Headquarters and Headquarters Troop, 14th Squadron, 4th Cavalry.