Harrison led divisional advanced party overseas by the end of January 1944 and spent several next months with intensive training in England.
The 30th Infantry Division departed for France in June that year and landed at Omaha Beach, Normandy on June 11, 1944.
Harrison participated in the combats at Vire-et-Taute Canal and on Vire River and quickly won the admiration of his troops by accompanying them on the front lines with M3 submachine gun in hand.
He also spent a first night in France in the trench with combat troops.

On July 25, 1944, the 30th Infantry Division still participated in the combats near Saint-Lô, which it secured few days earlier.
The Division was subsequently scheduled to participate in Operation Cobra, an offensive with intention to advance into Brittany.
The offensive was to begin with a major saturation bombing of the enemy with the troops then moving in afterward, but due to the inaccurate plane navigation, planes bombed erroneously their own men.
More than 600 of the men had been hit, many killed, including lieutenant general Lesley J. McNair, Commander of Army Ground Forces.

Even Harrison's command group was located in the rear, he returned deliberately to the forward area shortly before the bombing began.
He was thrown down by the blast of German Artillery fire, but was unharmed.
Realizing that the success of the entire operation depended on the 30th Infantry Division carrying out its mission, Harrison began analyzing the situation and found out, that divisional Sherman tanks were totally disorganized and demoralized infantry was spread in the area.
Moreover commanding officer of 120th Infantry Regiment, Colonel Hammond D. Birks was located somewhere in the forward area and his jeep was knocked out.

Harrison ordered commander to get his tanks in battle formation and get ready for action and evacuated Colonel Birks to safety.
He took soldier with bazooka through the hedgerow and ordered him to attack the German tank nearby.
The soldier had hit German tank several times, but panicked and ran into the open, where he was killed.
Harrison crawled back and came upon four American tanks in a neighboring field, who were waiting out the enemy shelling with their hatches shut tight.
He climbed on the commander's tank and forced the crew to open the hatch by beating the tank's turret, subsequently ordering the general attack, which was successful.
For his heroism in action, he was decorated with Distinguished Service Cross, the second highest decorations of the United States military for valor in combat.

Harrison then participated in the Battle of Mortain, German drive to Avranches in mid-August 1944 and 30th Division clashed with elite 1st SS Panzer Division Leibstandarte SS Adolf Hitler.
The 30th Division then advanced through Belgium and Harrison distinguished himself again on September 2, 1944, while leading the Task Force of his division.

He was riding with the forward elements of his Task Force heading to Rumilly, when his column was ambushed by enemy tanks.
The Harrison's jeep was hit in the radiator and he was struck by enemy 75mm tank shell, hitting him to right shoulder, arm and leg.
Harrison escaped from the damaged vehicle and hit the ditch, where he immediately dispatched his aide and driver to contact the next ranking officer in order that he might continue the advance.
He did not mention his wounds, which were not visible due to his raincoat and crawled approximately 600 yards to the rear of the column in order to give further instructions for continuing the mission.

Harrison fainted momentarily due to his wounds, but refused to be evacuated until he had contacted his subordinates and instructed them in the continuation of the attack.
By the time, General Hobbs arrived and following a discovery of Harrison's wounds, he ordered his evacuation.
For bravery in action, he was decorated with Silver Star and also received Purple Heart for wounds, which he was most proud of.

He spent a week in First Army Hospital in Versailles and rejoined his division in Belgian town of Tongres, where the division'
Harrison led divisional advanced party overseas by the end of January 1944 and spent several next months with intensive training in England. The 30th Infantry Division departed for France in June that year and landed at Omaha Beach, Normandy on June 11, 1944. Harrison participated in the combats at Vire-et-Taute Canal and on Vire River and quickly won the admiration of his troops by accompanying them on the front lines with M3 submachine gun in hand. He also spent a first night in France in the trench with combat troops.
On July 25, 1944, the 30th Infantry Division still participated in the combats near Saint-Lô, which it secured few days earlier. The Division was subsequently scheduled to participate in Operation Cobra, an offensive with intention to advance into Brittany. The offensive was to begin with a major saturation bombing of the enemy with the troops then moving in afterward, but due to the inaccurate plane navigation, planes bombed erroneously their own men. More than 600 of the men had been hit, many killed, including lieutenant general Lesley J. McNair, Commander of Army Ground Forces.
Even Harrison's command group was located in the rear, he returned deliberately to the forward area shortly before the bombing began. He was thrown down by the blast of German Artillery fire, but was unharmed. Realizing that the success of the entire operation depended on the 30th Infantry Division carrying out its mission, Harrison began analyzing the situation and found out, that divisional Sherman tanks were totally disorganized and demoralized infantry was spread in the area. Moreover commanding officer of 120th Infantry Regiment, Colonel Hammond D. Birks was located somewhere in the forward area and his jeep was knocked out.
Harrison ordered commander to get his tanks in battle formation and get ready for action and evacuated Colonel Birks to safety. He took soldier with bazooka through the hedgerow and ordered him to attack the German tank nearby. The soldier had hit German tank several times, but panicked and ran into the open, where he was killed. Harrison crawled back and came upon four American tanks in a neighboring field, who were waiting out the enemy shelling with their hatches shut tight. He climbed on the commander's tank and forced the crew to open the hatch by beating the tank's turret, subsequently ordering the general attack, which was successful. For his heroism in action, he was decorated with Distinguished Service Cross, the second highest decorations of the United States military for valor in combat.
Harrison then participated in the Battle of Mortain, German drive to Avranches in mid-August 1944 and 30th Division clashed with elite 1st SS Panzer Division Leibstandarte SS Adolf Hitler. The 30th Division then advanced through Belgium and Harrison distinguished himself again on September 2, 1944, while leading the Task Force of his division.
He was riding with the forward elements of his Task Force heading to Rumilly, when his column was ambushed by enemy tanks. The Harrison's jeep was hit in the radiator and he was struck by enemy 75mm tank shell, hitting him to right shoulder, arm and leg. Harrison escaped from the damaged vehicle and hit the ditch, where he immediately dispatched his aide and driver to contact the next ranking officer in order that he might continue the advance. He did not mention his wounds, which were not visible due to his raincoat and crawled approximately 600 yards to the rear of the column in order to give further instructions for continuing the mission.
Harrison fainted momentarily due to his wounds, but refused to be evacuated until he had contacted his subordinates and instructed them in the continuation of the attack. By the time, General Hobbs arrived and following a discovery of Harrison's wounds, he ordered his evacuation. For bravery in action, he was decorated with Silver Star and also received Purple Heart for wounds, which he was most proud of.
He spent a week in First Army Hospital in Versailles and rejoined his division in Belgian town of Tongres, where the division'
William Kelly Harrison Jr.