Most Vietnam War operations are remembered for specific engagements — helicopter insertions into hot landing zones, firefights at named hills. Operation Washington Green was different. It was a philosophy as much as a campaign. The 173rd Airborne's mission unfolded on three simultaneous fronts: pursuing pacification plans laid down by the South Vietnamese government, upgrading the combat effectiveness of South Vietnamese regional and popular forces, and conducting conventional operations that could reinforce the other two efforts. Every US rifle company was collocated with a Regional Force counterpart. Every rifle platoon worked alongside a Popular Force platoon. Artillery liaison teams were embedded at district fire direction centers. Battalion intelligence officers sat shoulder to shoulder with District Intelligence Coordination Center staff. The intent was integration — American firepower and South Vietnamese legitimacy, fused together at every level of command. Whether that fusion ever truly took was the question the operation spent twenty-one months trying to answer.

Through August 1969 the brigade ran extensive cordon-and-search operations across the populated coastal lowlands, working with Regional Force and Popular Force units to root out Viet Cong infrastructure and guerrillas. Night patrolling became the standard tempo. The initial phase produced 438 enemy killed, 54 captured, and 152 small arms seized — the kind of numbers that looked like progress. But the terrain inland was a different story. In early February 1970, soldiers from the 3rd Battalion, 506th Infantry Regiment found an extensive cave complex in the high ground near My Binh Hamlet, Tam Quan District, where elements of the North Vietnamese 22nd Regiment had positioned themselves for a Tết offensive. Artillery, tactical air strikes, and CS gas all proved unable to dislodge the defenders. What finally worked was fougasse: 55-gallon drums of jellied fuel, dropped into the cave entrances. The North Vietnamese came out. Eighty-five were killed in that engagement alone.

As Washington Green expanded into its second and third phases, the operational area shifted toward the contested highland valleys west of Highway 1. The Kim Son Valley — known to U.S. planners as the Crow's Foot, and to North Vietnamese commanders as Base Area 226 — was a major logistics corridor and staging ground for the PAVN 3rd Division. The 3rd Battalion, 503rd Infantry Regiment conducted reconnaissance-in-force missions there, while the 3rd Battalion, 506th Infantry provided covering pressure. In spring 1970 the operation's tempo shifted further: ARVN forces from the brigade's area of operations were dispatched into Cambodia following the fall of the Sihanouk government, and US battalion areas expanded to cover the gaps. The training of Regional and Popular Force units accelerated. More patrols. More ambushes. The numbers from Washington Green III alone — 938 enemy killed, 383 weapons captured, 30 Chieu Hoi (defectors accepted under the amnesty program) — told one kind of story.

Operation Washington Green concluded on 1 January 1971. Total PAVN and Viet Cong losses across all phases were counted at 1,957 killed. Those numbers were real — each represented a fighter who would not return to the battlefield. But the operation's own stated goal had never been the enemy death toll. It had been the pacification of Bình Định Province, the transfer of security responsibilities to South Vietnamese forces capable of holding them, the creation of conditions stable enough that ordinary people could live without fear of either side. The brigade's senior officer debriefing report, filed in August 1970, documented the tactical results carefully. The political results — whether the people of those four northern districts had been won over, whether the South Vietnamese government had truly taken hold — were harder to quantify, and history's verdict on that question would not arrive for another four years.