This was one of Harley's ads in a campaign right after WWII to attract the returning GI's from overseas to buying a Harley.
The strong military resemblence in the rider's clothing was a direct ploy by HD's advertising folks to attract the former military personnel. Lots of troops rode Harleys during military service as scouts, couriers, and military police, Harley was trying to get them onto civilian bikes.
The ad campaign was highly successful as a lot of GI's returning from the war had a chunk of 'mustering out pay' and buying a motorcycle was certainly cheaper than buying an automobile. Plus... many of the battle hardened troops were not ready to settle down to a mundane, boring lifestyle so the image of blasting down the highways on a Harley was a powerful incentive that sold lots of Harleys for the motor company when they were trying to get back heavily into the civilian market following the end of military contracts.