As the 1940s opened, the nation prepared for the inevitable entry into the war in Europe. Colonel Lynn Black and Patrol administrators already expected a redirection of activities, but unfortunately, the reality would far exceed expectations.

The Division already had taken on a few wartime duties, beginning in 1939 when the Federal Bureau of Investigations (FBI) requested the Patrol's assistance in investigations of un-American activities. A flood of these requests began pouring in and by 1943, 635 cases, consuming 31,000 man-hours, had been completed for the FBI. Most involved routine intelligence gathering of persons reported as "suspicious."

In February 1941, the Commanding General of the Fifth Corps Area of the U.S. Army called on the Division to coordinate the movement of military and civilian traffic in the state. He appointed Col. Black "traffic liaison officer" later that year and, under his direction, Ohio was the first state in the nation to complete plans for the rapid mobilization of troops and equipment. In 1941 alone, 154 convoys moved across Ohio under the direction of the Patrol.

Other changes came in the form of new legislation. In May 1941, the Patrol's powers and duties reformed to include jurisdiction over all rural roads (including the power to make felony arrests), and not just the state highway system. This also maintained that it was the duty of the OSHP to investigate all accidents outside municipal borders.

Foreseeing the impact of the war in Europe, Governor John W. Bricker noted in 1941 that either the Highway Patrol had to be given full powers of arrest, or an "Ohio State Guard" would be necessary. Bricker actually favored the first option, stating it would be less expensive. "One patrolman," he said, "would be worth several guardsmen, and could be mobilized faster."

Bricker also cited the possibility that a guard force would be trained at great expense only to be demobilized shortly after the war, whereas a patrolman's training would benefit taxpayers for years.