This study uses discontinuities in U.S. strategies employed during the Vietnam War to estimate their causal impacts. It identifies the effects of bombing by exploiting rounding thresholds in an algorithm used to target air strikes. Bombing increased the military and political activities of the communist insurgency, weakened local governance, and reduced noncommunist civic engagement. The study also exploits a spatial discontinuity across neighboring military regions that pursued different counterinsurgency strategies. A strategy emphasizing overwhelming firepower plausibly increased insurgent attacks and worsened attitudes toward the U.S. and South Vietnamese government, relative to a more hearts-and-minds-oriented approach.

This is from Melissa Dell and Pablo Querubin, “Nation Building Through Foreign Intervention: Evidence from Discontinuities in Military Strategies,” Quarterly Journal of Economics, December 21, 2017.

One excerpt:

The overwhelming firepower approach can be summed up by the Vietnam-era adage: “get the people by the balls and their hearts and minds will follow” (Kodosky 2007, p. 175). Military strategy emphasized that overwhelming firepower could reduce insurgent forces, disrupt operations, and crush morale. According to General William DePuy: “The solution in Vietnam is more bombs, more shells, more napalm” (Sheehan 1988, p. 619). Civilian strategists advocated that coercion could also incentivize citizen compliance, with National Security Adviser Walt Rostow arguing that countering communism required “a ruthless projection to the peasantry that the central government intends to be the wave of the future” (Milne 2008, p. 88). In contrast, skeptics highlighted that insurgents were difficult to locate and that overwhelming firepower could backfire if civilians were hit instead. It could create grievances that inspired citizens to join the insurgency and could widen the political legitimacy gap between the insurgents and the South Vietnamese government. As James Scott (1985, 2009) argues, a coercion-oriented approach will be ill-suited to gaining cooperation if citizens have many ways to undermine a state they do not genuinely support.