This is an eight-volume study undertaken by The BDM Corporation under contract to the U.S. Army. The multi-faceted research effort was meant to detail the major military and political decisions made by the U.S. during its involvement in Southeast Asia, to assess the merits of those decisions, and to derive useful insights and general lessons regarding the U.S. experience in Vietnam.
The links below take you a DTIC landing page. From there, click on the pdf link to view the full document.