Chapter 5 assesses US air power following the Tet Offensive through the cross-border incursion into Cambodia in 1970. The newly elected US president, Richard Nixon, sought an American withdrawal from South Vietnam. However, he initially expanded the conflict into Cambodia to deny the NVA/VC sanctuary and sever their southern supply lines. Leading up to the invasion, the Commando Hunt air interdiction campaign in southern Laos slowed the movement of supplies. It also imposed substantial costs on the North to keep the Ho Chi Minh Trail open. Commando Hunt could not halt the NVA troops from making the journey to South Vietnam on foot, but the direct attack of fielded forces in South Vietnam and Cambodia did continue to keep the NVA/VC dispersed and hidden. Keeping the North Vietnamese on the defensive provided the time and space for South Vietnam’s pacification program to take root and for the Vietnamization program to generate conventional capabilities for the Army of the Republic of Vietnam (ARVN) to replace withdrawing American combat troops.

Looking at the Korean and Vietnam Wars, we evaluate the influence of casualties disaggregated by space/hometowns and time on mass opinion in both the Korean and Vietnam wars and on individual opinion in the Vietnam War. We find a powerful connection between US casualties and public support for a war consistent with our expectations about the importance of casualty trends, the geographic locations of casualty hometowns, and the interaction of these dynamics. Disaggregated casualties are better able to capture variation in mass public and individual wartime opinion than are logged cumulative national casualties – the standard wartime measure employed. We also find that the wartime information-opinion process operates more strongly in the ex ante identifiable early stages of a conflict, and less effectively later in a conflict when casualty expectations (and thus the value of new information) begin to harden. These results strongly support the general notion that casualty patterns act as an observable proxy for our RP/ETC process by capturing information that individuals draw on to generate ETC and formulate wartime positions, improving our ability to understand and predict wartime opinion.