Ever wondered what this symbol means? Army regulation AR-850-5 issued August 1942 ordered a plain white five pointed star, as the national symbol, it was seen in all theatres from 1943 and by 1944 was the most common national identification sign. In armored units, the white star was often painted out, or a circle around the star was added to avoid looking like a German cross at distance. Additionally, the circle was to distinguish between vehicles that had been sent oversees as part of the Lend Lease Act and did not have the white circle, and which vehicles were being used by American troops.
The invasion star symbol has the circle interrupted by lines at the points of the star. This is because the painting of the circle would often be done with a stencil on the field. It was meant to be filled in to create a full circle, but these “lazy circles” were often left. – Americangimuseum.org