United States military insignia

From Memory Alpha, the free Star Trek reference.

United States military insignia is that insignia which was used by the United States armed forces to display rank.

General rank	insignia example	historical examples
4 star general		General Norman Schwarzkopf, US Army
3 star general		Lt. General Rex Denning, US Army Air Corps
2 star general		—
1 star general		—

One and two star generals have never been seen on screen, but their existence is implied by the appearance of three and four star generals. Two additional ranks, "General of the Army" (five star) and "General of the Armies" (six star), have been held by Douglas MacArthur and George Washington respectively, but the insignia for these ranks has never been seen or discussed.

Officer rank	insignia example	historical examples
colonel		Stephen G. Richey, US Air Force
lieutenant colonel or commander		Commander Rogerson, US Navy
		Lieutenant Colonel Fellini, US Air Force
major		US Army Air Corps major, 1947
captain or lieutenant		Captain John Christopher, US Air Force
		Cetacean Institute tourist
first lieutenant		US Marine Corps lieutenant, USS Enterprise (CVN-65)

The United States officer ranks of second lieutenant, ensign, lieutenant j.g., lieutenant commander, and the rank of naval captain have never been seen or discussed in Star Trek, hence their omission from the above table.

Enlisted rank	insignia example	historical examples
first sergeant		Marine Corps Security Commander, USS Enterprise (CVN-65)
master sergeant		---
staff sergeant		Air Police Sergeant, US 498th Airbase Group, Omaha, Nebraska
sergeant		---
petty officer		Navy Electronics Technician
corporal		San Francisco tourist
private	–	–
airman	–	Security policeman, US 498th Airbase Group, Omaha, Nebraska

The above United States armed forces insignia have appeared in various Star Trek productions including TOS: "Tomorrow is Yesterday", TOS: "Miri", Star Trek IV: The Voyage Home, DS9: "Little Green Men", VOY: "The Killing Game, Part II", and ENT: "Storm Front, Part II".