The long war in Vietnam left an indelible mark on the fabric of innumerable elements of American life. It shaped elements of America's military and political debates for decades following the end of the war. Its divisiveness and polarising impact generated a profound cultural shift in some quarters, which subsequently bled over into literature, film and, more generally, the contested nature of the national memory. The nature of the fighting, and the general character of the war, was a harbinger for the types of challenges that would come to dominate America's wars in the late twentieth and early twenty-first centuries: asymmetric, both conventional and ‘among the people’, and to a greater or lesser extent, reliant upon good intelligence for their effective prosecution. Just as with more contemporary wars, the intelligence war in Vietnam has generated several narrative strands that dominate the popular imagination: paramilitarism and violence, controversy and politicisation, and accusations of profound failure. Some of these narratives withstand historical scrutiny, others do not. But the scope of the intelligence war in Vietnam is both broader and deeper than credited in the popular imagination.

The historiography of US intelligence, and the CIA in particular, in Vietnam and South East Asia more broadly is well developed, and has continued to grow over recent years. Elements of it have been immortalised in fiction, most notably from the early days of US involvement in Indochina in Graham Greene's The Quiet American, published in 1955. And the intelligence element has, of course, been a staple feature of general histories of the war for decades owing, in no small part, to the very public controversies that surrounded it. More recent histories have benefited from greater perspective – for example, from the memoirs of key CIA individuals – and from access to declassified materials that have been published by the US government. These include John Prados’ study of the war, published in 2009, which offers an illuminating perspective on the CIA's evolving role in the conflict. These general histories of the war have also been supplemented with volumes focused on the CIA and its work more specifically; some, such as Tim Weiner's Legacy of Ashes, offer a very critical perspective.