The United States adopted a national insignia for all military aircraft in May 1917 using the colors specified for the U.S. flag, consisting of a white five-pointed star inside of a blue circumscribed circle, with a red circle in the center of the star having a diameter tangent to the pentagon of the interior points of the star. The insignia was ordered painted on both wingtips of the upper surface of the top wing, the lower surface of bottom wings, and the fuselage of all Army aircraft on 17 May 1917. However due to concerns about confusion with the markings of enemy aircraft, in early 1918 a red, blue, and white roundel similar to those used by the Allied Powers, in the former color arrangement of the defunct Imperial Russian Air Service, was instead ordered painted on all U.S. aircraft operating in Europe, remaining in effect until 1919.