18th Pursuit Group (18th PG) / 18th Fighter Group (18th FG)
U.S. Army Air Force (USAAF), 13th Air Force (13th AF)

Background
The 18th Pursuit Group (18th PG) was assigned to the 7th Air Force (7th AF) in Hawaii. During May 1942, redesignated 18th Fighter Group (18th FG) was assigned to the 13th Air Force (13th AF) in the South Pacific (SOPAC). The 18th FG was comprised of the 12th Fighter Squadron (12th FS), 44th Fighter Squadron "Vampire Squadron" (44th FS).

12th Fighter Squadron (12th FS)
The 12th Fighter Squadron (12th FS) operated the P-38 Lightning and P-39 Airacobra in the South Pacific (SOPAC).

44th Fighter Squadron (44th FS) "Vampire Squadron"
The 44th Fighter Squadron (44th FS) nicknamed "Vampire Squadron" operated the P-40 Warhawk and later P-38 Lightning.

70th Fighter Squadron (70th FS)
The 70th Fighter Squadron became part of the 18th Fighter Group on March 30, 1943 until deactivated December 26, 1945.

73rd Fighter Squadron (73rd FS)
The 73rd Fighter Squadron (73rd FS) was part of he 18th Fighter Group until October 15, 1942 the to 318th Fighter Group (318th FG).

References
HQ 18th Fighter Group January 1 – February 29, 1944 (USAF Historical Research Agency IRSUM: 78048)