In November, 1965, the 20th Helicopter Squadron was reorganized at Eglin AFB, Florida, under the command of Lt. Col. Lawrence Cummings. Pilot and maintenance crews were given training and then transferred to Tan Son Nhut AB, South Vietnam. The 14 CH-3C helicopters were disassembled, flown on C-133 MAC cargo planes to Tan Son Nhut, and then assembled by 20th personnel. The 20th began combat missions out of Tan Son Nhut in December, 1965.  Early in 1966, the squadron was then split into several groups; one remaining at Tan Son Nhut, one at Da Nang AB and one at Nha Trang AB. In February two CH-3Cs from Tan Son Nhut were sent to Nakhon Phanom .  In April, 1966, the unit at Nha Trang was transferred to Udorn AB, Thailand, and in May, 1966, the unit at Da Nang also moved to Udorn. The 20th's mission at Udorn was to transport Thai military and police for counter-terrorist and counterinsurgency operations. Since many of these missions involved flying into Laos, the CH-3C's did not display any US markings or insignias.  During this period at Udorn, 676, the "Black Mariah joined the 20th and it is believed this is where it was painted black.   By June of 1966, most of the 20th's operations were concentrated in Udorn, with only a single flight at Tan Son Nhut.   In June of 1967, 15 UH1F/P Hueys were transferred to the 20th at Tan Son Nhut from the 606th Air Command Squadron at NKP.   This unit became known as the "Green Hornets."  It was later in '67 that the CH-3Cs were upgraded with the more powerful -5 engines, and were designated CH-3Es.   By the beginning of 1968, all of the 20th's CH-3Cs had been moved to Udorn.   In the spring of 1968, some CH-3Cs were transferred to NKP to start up the 21st Special Operations Squadron, the "21st SOS."   By July of '68, the 20th was down to 10 CH-3Es, and maintenance problems reduced that number to 5 or 6 at times.   As a result, a flight of 4 Hueys were sent from Nha Trang to Udorn, however they didn't have the range for most cross-border operations.   In August, 1968, the 20th Helicopter Squadron was re-designated the 20th Special Operations Squadron, the 20th SOS.   On August 1, 1969, the CH-3Es and the Pony Express mission were transferred to the 21st SOS.   Left with only a few Hueys, they returned to Vietnam to join the Green Hornets, which in September moved from Nha Trang to Tuy Hoa.

On April 1,1972 the 20th SOS was deactivated.

For more info on the 20th Helicopter squadron, visit the 
                 USAF Helicopter Pilots Assoc.