At the time of Japanese Attack on Pearl Harbor, on December 7, 1941, Roberts served as acting commander of 3rd Defense Battalion in the absence of Colonel Pepper, who was on an observation tour of Higgins Boats near Midway.
Roberts was sleeping in his quarters in Honolulu when he was woken up by a telephone call made by the battalion's assistant communication officer, Frederick M. Steinhauser.
He was quickly briefed by Steinhauser and jumped into his car with Major Kenneth W. Benner, commanding officer of the battalion's 3-inch antiaircraft group.

They drove through the heavy traffic toward Pearl Harbor, witnessing Japanese planes attacking the Navy ships.
Roberts reached the Marine Barracks at Pearl Harbor Navy Yard after a twenty minute trip and began organizing the anti-aircraft defense of his battalion.
He directed medical personnel to set up dressing stations at each battalion headquarters; organized the precautions in the temporary wooden barracks, placing extinguishers in the front of them, along with shovels, axes and buckets of sand (the latter to deal with incendiary bombs); hose reel and chemical carts placed near the center hydrant near the mess hall; and all possible containers filled with water for both fighting fires and drinking.

In addition, he ordered cooks and messmen to prepare coffee and fill every other container on hand with water, and organized riflemen in groups of about 16 to sit on the ground with an officer or non-commissioned officer in charge to direct their fire.
He also called for runners from all groups in the battalion and established his command post at the parade ground's south corner, and ordered the almost 150 civilians who had showed up looking for ways to help out to report to the machine gun storeroom and fill ammunition belts and clean weapons.
Among other actions, he also instructed the battalion sergeant major to be ready to safeguard important papers from the headquarters barracks.
Roberts directed anti-aircraft defense and subsequent fire extinguishing and recommended that the entire 3d Defense Battalion be commended for "their initiative, coolness under fire, and the alacrity with which they emplaced their guns."
At the time of Japanese Attack on Pearl Harbor, on December 7, 1941, Roberts served as acting commander of 3rd Defense Battalion in the absence of Colonel Pepper, who was on an observation tour of Higgins Boats near Midway. Roberts was sleeping in his quarters in Honolulu when he was woken up by a telephone call made by the battalion's assistant communication officer, Frederick M. Steinhauser. He was quickly briefed by Steinhauser and jumped into his car with Major Kenneth W. Benner, commanding officer of the battalion's 3-inch antiaircraft group.
They drove through the heavy traffic toward Pearl Harbor, witnessing Japanese planes attacking the Navy ships. Roberts reached the Marine Barracks at Pearl Harbor Navy Yard after a twenty minute trip and began organizing the anti-aircraft defense of his battalion. He directed medical personnel to set up dressing stations at each battalion headquarters; organized the precautions in the temporary wooden barracks, placing extinguishers in the front of them, along with shovels, axes and buckets of sand (the latter to deal with incendiary bombs); hose reel and chemical carts placed near the center hydrant near the mess hall; and all possible containers filled with water for both fighting fires and drinking.
In addition, he ordered cooks and messmen to prepare coffee and fill every other container on hand with water, and organized riflemen in groups of about 16 to sit on the ground with an officer or non-commissioned officer in charge to direct their fire. He also called for runners from all groups in the battalion and established his command post at the parade ground's south corner, and ordered the almost 150 civilians who had showed up looking for ways to help out to report to the machine gun storeroom and fill ammunition belts and clean weapons. Among other actions, he also instructed the battalion sergeant major to be ready to safeguard important papers from the headquarters barracks. Roberts directed anti-aircraft defense and subsequent fire extinguishing and recommended that the entire 3d Defense Battalion be commended for "their initiative, coolness under fire, and the alacrity with which they emplaced their guns."
Harold C. Roberts