In response, on 5 April, 1972, the 1^st Marine Air Wing, Fleet Marine Force Pacific, principally located at MCAS Iwakuni Japan and MCAS Futema, Okinawa, was directed by Navy Command Seventh Fleet to deploy two tactical aircraft squadrons to the Republic of Vietnam.  Marine Air Group-15 was immediately ordered to mobilize their two F-4 Phantom squadrons [VMFA-115 and VMFA-232], along with supporting units, to Da Nang Air Force Base, South Vietnam, from MCAS Iwakuni to help counter the invasion forces. They were joined by MAG-12’s F-4 Phantom squadron [VMFA-212] from Kaneohe Bay, Hawaii 9 days later.

While the Marines were conducting air operations from Da Nang, President Nixon’s administration was trying to reconcile its overall “Vietnamization” plan that, as part of the peace negotiation efforts and American force withdrawal, had removed the Marines from the Vietnam combat theater a year earlier. The administration decided the Marines were again necessary, but couldn’t stay in Vietnam. 

However,  where else to deploy was a problem. Political constraints with Tokyo prevented SEA combat operations direct from Japan, and the Navy and Air Force bases in the Philippines, and Air Force Bases in adjacent Thailand were already at (or given other unit mobilizations, soon would be at) capacity. Somebody back at the Pentagon noted there was an airfield originally constructed in 1967 for the Air Force 60 miles south of Udon Thani at Nam Phong, Thailand that was only being used covertly by Army "Green Beret" special forces for training Thai and Laotian counter-insurgents - the USAF TC-121 squadron originally planned for Nam Phong in 1968  was instead deployed to RTAFB Korat (Nakhon Ratchashima) 135 air miles to the south.

On 17 May, 1972 as combat operations continued around the clock at Da Nang,  a USMC/USN survey team dispatched to Nam Phong to evaluate suitability.

Five days later, on 22 May, 1972, “Task Force Delta” was born.   

In spite of a general chaotic US military force mobilization throughout the Pacific in response to the “Easter Offensive”, the DoD pulled out all the stops they could for the Marines, allocating Navy transport ships and the 5th NMCB “SeaBees”, Army convoys from the port in Sattahip, MATCU-62 setting up local Air Traffic Control facilities for all the Air Force C-141's and C-5s augmenting the Marines advance teams, Hotel and Lima companies of  3^rd Battalion/9^th Marines from Okinawa for base security, and VMGR-152's C-130s and KC-130s transitioning in and out and providing in-air refueling, to ready the base for expedition operations. This included expanding the ramp area with steel-matting, bull-dozers for clearing jungle for tents, setting up "6-holer" latrines, bringing in generators, food and water supplies, laying barb-wire and digging bunkers, all during the monsoon season. 
As Task Force Delta's outpost was going operational, VMFA-212 stood detached and retrograded from Da Nang back to Kaneohe Bay on 18 June 1972.

On 17 June the F-4 Phantoms of VMFA-115, having arrived the day earlier, were refueled and rearmed and commenced combat operations from the "Rose Garden" as VMFA-232 arrived. VMFA-232 commenced combat operations on 20 June as the Task Force welcomed  VMA(AW)-533’s A-6a Intruders from Mag-12 into their midst, the all-weather A-6a's commencing combat operations immediately. Task Force Delta mobilization was complete (although the base itself, incrementally improved as combat operations and resources allowed, never would be).

Nobody knew at the time, but 15 months later, after virtually continuous 24 /7 combat operations in Vietnam, Cambodia and Laos, Task Force Delta would be the last Marine Combat force to stand down and leave the Vietnam War theater. 

And at the time, very few even knew they were there at all.

(In fact, Marine Corps combat aircraft suddenly appearing in airspace transversed by Thailand-based US Air Force units
created some exciting encounters in mid-72, highlighting the need to "spread the word" and share comm frequencies.)