The inscription of art work on military planes dates to World War I, when paintings were usually extravagant company or unit insignia. However, regulations were put in place after the war to stymie the practice.
As the United States entered World War II, nose art regulations were relaxed, or in many cases totally ignored. WWII would become the golden age of aircraft artistry.
Artwork was typically painted on the nose of the plane, and the term “nose art” was coined.
Nose art was a morale booster, and those in daily combat needed that boost. Facing the prospect of death on every flight, the crew deserved all of the encouragement, and smiles, available to them.
The art on the plane unified the crew, and identified it, and made it unique from all of the aircraft in their unit or on their base.