Operation Thayer II — The Long Binh Dinh Campaign (Oct 1966 – Feb 1967)
Operation Thayer II — the long Binh Dinh campaign
Context page — operation level. Built from the 1st Cavalry Division's own Operational Report — Lessons Learned for the quarter ending 31 January 1967, the report that covers this campaign, with the tail of the previous quarter's ORLL for its opening. It frames the operation that D Company, 2/8 Cavalry fought through into early 1967 — the operation in which CPL Peter Keller and CPL Donald Yates were killed on 28 January 1967 in the Kim Son Valley. Division- and brigade-level movements are well documented; D Company's hour-by-hour positions await the battalion staff journal.
What it was
Operation Thayer II (24 October 1966 – 12 February 1967) was the continuation of Operation Irving and the third and longest phase of the 1st Cavalry Division's autumn-and-winter campaign in eastern Binh Dinh Province. By the end of January 1967 the division reported it as its longest operation in Vietnam to that date and the one accounting for its highest enemy body count. Across the full campaign, North Vietnamese and Viet Cong losses were reported at roughly 1,757 killed, against 242 Americans killed and 947 wounded.
The operation was a sustained search-and-destroy and pacification effort, not a single battle. The division ORLL lists its significant contacts on 1 December, 17 December, 27 December, and 27 January, and notes that Thayer II was marked by a heavy interdiction program — built on more target intelligence "than ever before because 1st Cavalry units have been operating in the area since 13 September" (i.e., since Thayer I) — plus extensive use of artillery raids and SS-11 missiles against bunkers and caves. Intelligence work was a campaign in itself: the division captured the complete Letter Box Numbers and rosters of the 18th NVA Regiment and exploitable prisoners and documents from the 22d NVA Regiment, and on 19 January found a huge tunnel-and-cavern complex (vic BR740748) believed to be the VC Binh Dinh Province headquarters.
Where 2/8 Cavalry — and D Company — fit
2/8 Cavalry fought Thayer II as a 1st Brigade battalion under LTC Thomas H. Tackaberry (until LTC John C. Dashiell relieved him on 7 February 1967, days before the operation closed). From 3 January 1967 the 1st Brigade held the Central and Southern Kim Son Valley as its area of operations. The battalion's firebase records place its companies in a cluster of landing zones there that month — D Company at LZ Minh (BR707760), B Company at LZ Ho, and C Company at LZ Chi.
It was in this setting that D Company lost two men on 28 January 1967 — CPL Peter Joseph Keller Jr., 21, of Detroit, and CPL Donald Francis Yates, 20, of Round Lake, New York — both to multiple fragmentation wounds, their Wall lines three apart, the signature of a single shared contact. Their deaths are documented on the 28 January 1967 contact page. The action fell below the division's significant-contact threshold and is not separately narrated in the ORLL, so the landing zone, the nature of the contact, and the enemy unit all remain to be pinned.
At the battalion level over those two days, 2/8 Cavalry lost a third man — PFC Jose J. Boyless of A Company, killed 27 January — recorded here as part of the Thayer II aggregate; he is not a D Company loss and has no profile in this archive.
A word of caution on the calendar: the division's named 27 January fight — often the one that turns up first in the record — was a different action: 2/12 Cavalry (2nd Brigade) against the 8th Battalion, 22d NVA Regiment northeast of Bong Son (vic BS910055), which a 28 January sweep closed out with 72 NVA dead and 11 prisoners. That was not 2/8 Cavalry and not the Kim Son cluster, and the two should not be conflated.
What's still open
The division ORLL is written at division and brigade level, so D Company's specific daily positions within Thayer II — and the day-of detail of the 28 January action — are not in it. Those await the 2/8 Cav daily staff journal (NARA RG 472); confirmation of LZ Minh as the 28 January position would also trigger a dedicated LZ Minh location page.
Help us complete the record
If you served with D Company, 2/8 Cavalry during Operation Thayer II, or knew Peter Keller or Donald Yates, please reach us through the contribute form.
If you served with D Company, 2/8 Cavalry during Operation Thayer II, or knew CPL Peter Keller or CPL Donald Yates, we'd like to hear from you — especially anyone who can describe the Kim Son Valley positions or the 28 January 1967 action.
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