How should a state which lacks the monopoly of violence go about acquiring it? We investigate the use of high-powered incentives for members of the Colombian army as part of a strategy to combat left-wing guerillas and build the state's monopoly of violence. We show that this top-down state-building effort produced several perverse side effects. Innocent civilians were killed and misrepresented as guerillas (a phenomenon known in Colombia as 'false positives'). Exploiting the fact that Colombian colonels have stronger career concerns and should be more responsive to such incentives, we show that there were significantly more false positives during the period of high-powered incentives in municipalities where a higher share of brigades were commanded by colonels and in those where checks coming from civilian judicial institutions were weaker. We further find that in municipalities with a higher share of colonels, the period of high-powered incentives coincided with a worsening of local judicial institutions and the security situation, with more frequent attacks not just by the guerillas but also by paramilitaries.Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.