At least Sergeant.
That's the minimal rank soldiers have in the special forces.
According to John Rambo's Dossier in the Ultimate Edition of the Rambo Movies it states that he was promoted in the field to a Sergeant during the Vietnam War
A handwritten signature normally contains only first initials or forename, and surname. A printed signature or signature block may read, "J. Smith, Major, retired", "J. Smith, Major, retd", or "J. Smith, Major (retd)". The rank may also be abbreviated; e.g., Capt, Maj, Col, BGen, etc., depending on the degree of formality desired. Except in cases where the writer wishes to establish his/her qualification (e.g., a letter to the editor on a military matter), Captain is normally the least rank to appear as a postnominal honorific.
It is one rank below 2nd Lt. Here is a typical officer staff from archival records of 30th Mississippi Regiment, listed from company commander down to lowest officer rank. Company A, Neill Guards, of Carroll County,Captain - J. M. JohnsonFirst Lieutenant- J. W. S. MerrillSecond Lieutenant- J. T. StreaterThird Lieutenants- W. W. Conger, J. C. McMath.
Blackjack.
John "black-jack" Pershing
That was General John J. Pershing.
John J. Rambo. The 'J' is never expanded upon.
General of the Armies. A lifelong rank bestowed to him after retirement.
John J. Klein has written: 'Space warfare' -- subject(s): Military Astronautics, Space warfare
John J. Pershing
J. Arthur Rank was born on December 22, 1888.
J. Arthur Rank was born on December 22, 1888.
Lord J. Arthur Rank was born on December 22, 1888.
Lord J. Arthur Rank was born on December 22, 1888.
Lord J. Arthur Rank died on March 29, 1972 at the age of 83.
Washington held the rank of Lieutenant General (3-Star) until his death in 1799. In 1976 he was promoted posthumously to General of the Armies of the United States, the highest possible rank. Only Washington and Gen. John J. Pershing (1919) hold the rank of General of the Armies of the United States. During World War II the five-star rank of General of the Army was created. Both this and General of the Army of the United States are inferior to, and should not be confused with, General of the Armies of the United States.
John J. Pershing
General John J. Pershing, aka "Black Jack" Pershing.