Binh Dinh consisted of a narrow, heavily cultivated coastal plain with river valleys separated by ridges and low mountains reaching into the interior.

Rarely more than 25 km wide, it consisted of a series of small deltas, which often backed into gently rolling terraces some 30-90m in height, and, at irregular intervals, of a number of mountainous spurs from the highlands.

These spurs created narrow river valleys with steep ridges that frequently provided hideouts for PAVN/VC units or housed PAVN/VC command, control and logistical centers.

The heaviest rains had usually ended by December, but a light steady drizzle, which the French had called crachin weather and occasional torrential downpours could be expected to occur through March.

During the second, division elements would move to Bồng Sơn itself and launch a series of airmobile hammer-and-anvil operations around the plain and the adjacent valleys to flush the PAVN/VC toward strong blocking positions.

Meanwhile, Lt. Col. Robert McDade's 2nd Battalion, 7th Cavalry, with about 80 percent of its authorized strength and thus still not fully reconstituted after the fight at LZ Albany, boarded a dozen C-123s at the airstrip for the short ride into Bồng Sơn.

The rest of the battalion deployed without incident and then helicoptered north to Landing Zone Dog, where engineers started building an airstrip and digging in artillery.

In the meantime, PAVN/VC fire downed a CH-47 helicopter at Landing Zone Papa north of Bồng Sơn and Kampe responded by sending a 1/7th Cavalry company to secure the crash site.

Company A, 2/7th Cavalry understrength at two rifle platoons because of the crash three days earlier, entered the area at Landing Zone 2 and pushed north through rice paddies.

The sandy plain where it set down, Landing Zone 4, (14°31′48″N 109°01′26″E / 14.53°N 109.024°E / 14.53; 109.024) seemed safe, a relatively open tract in the hamlet of Phung Du 2 with a graveyard in its midst and tall palm trees on three sides.

When the second lift came ten minutes later however, the PAVN 7th Battalion, 22nd Regiment, entrenched in earthworks, palm groves and bamboo thickets throughout the hamlet, poured mortar and machine gun fire into the landing zone.

Company C commander, Captain Fesmire waved the second flight away, expecting the troops to be dropped at an alternative landing zone a few hundred meters to the southwest.

[7]: 207–8 After dawn on 29 January the low overcast lifted, and fighter-bombers pounded the area to McDade's north, detonating PAVN ammunition and causing large fires.

Beckwith was criticized for going into the An Lao valley, under VC control for 15 years, without South Vietnamese counterparts and ground intelligence and in poor weather.

On the morning of 15 February a platoon from Company B, 2/7th Cavalry, came under small-arms and mortar fire while patrolling about 4 km southeast of Firebase Bird, near the valley center.

Fire from Company B's mortar platoon, from helicopter gunships and Skyraiders and from artillery at Firebase Bird pounded the PAVN, then Diduryk's men attacked.

A smaller group attempted to escape southward but came under fire from the reserve platoon, which took many prisoners, including 93rd Battalion commander Lt. Col. Dong Doan who inadvertently provided his interrogators with enough information to identify the locations of both his regiment and its headquarters.

The move was triggered by Colonel Doan's revelation that the 2nd Regiment was operating in the mountains southeast of Pony, information that seemed to be confirmed when radio intercepts indicated the presence of a major PAVN/VC headquarters there.

The sweep force, 1/5th Cavalry, plus a battery of the 1st Battalion, 77th Artillery Regiment, helicoptered to Landing Zone Coil approximately 6 km northeast of Recoil.

During the action a psychological operations team circled overhead in a loudspeaker plane, broadcasting the message that further resistance would be futile and dropping safe conduct passes.

[7]: 213–4 Based on prisoner interrogations, American intelligence believed that the PAVN 6th Battalion, 12th Regiment was operating in the Cay Giep Mountains 5 miles (8.0 km) east of Bồng Sơn.

Eventually, additional air strikes opened holes in the jungle canopy wide enough to allow the men to reach the ground by scrambling down rope ladders suspended from the hovering helicopters.

Once deployed, the three battalions, soon joined by 1/5th Cavalry, searched the area and found little, although an ARVN unit near the Tra O Marsh killed about 50 PAVN who were attempting to flee the dragnet.

On 4 March, following word from South Vietnamese civilians that most of the PAVN had left the a rea around the end of February, Kinnard decided that the operation had run its course and over the next two days returned the 2nd Brigade to Camp Radcliff.

The plan was for the Marines to push southward into Binh Dinh province where they would meet the 1st Cavalry advancing northward in Operation Masher, trapping PAVN/VC forces between them.

He also said that Operation Double Eagle was a failure because it showed the people of the region that the Marines "would come in, comb the area and disappear; whereupon the VC would resurface and resume control.

[8]: 180  The 1st Cavalry listed as a success of the operation that "140,000 Vietnamese civilians volunteered to leave their hamlets in the An Lao and Son Long valleys to return to GVN control.

[8]: 204–5 Operation Masher-White Wing was considered a success by the Americans, demonstrating the capability of the helicopter-borne 1st Cavalry to conduct a sustained campaign against PAVN and VC forces and "to find, fix, and finish" the enemy.

[3]:chapter 4 An unknown number of people killed were civilians, and under the standard operating rules at the time those who did not 'voluntarily' leave free-fire zone were generally regarded as VC.

[11] A Joint Chiefs of Staff memo reported by The Wall Street Journal in 1966 urged President Johnson to "expand" the use of non-lethal chemicals in South Vietnam.