The 4th Corps is a field corps of the Turkish Land Forces. Its headquarters is in Ankara.
In 1974, it appears to have been part of the Second Army. Nigel Thomas's NATO Armies 1949-87, published in 1987, attributed the 4th, 8th, and 9th Corps to the Third Army.
In accordance with NATO's new strategy in the early 1990s, Turkey agreed to commit forces to NATO's ACE Rapid Reaction Corps. "Therefore, the decision was made to create a new division. Thus, the old 1st Infantry Division which had been abolished many years ago was reactivated and renamed as 1 TU Mech Inf Div and attached to 4 TU Corps on 30 November 1993."
References
4th Corps (Turkey) Wikipedia(Text) CC BY-SA