Chapter 2 argues that the combination of oil income and revolutionary politics generates systematic political incentives that increase a state’s aggressiveness and propensity to initiate international conflict, a phenomenon I call petro-aggression. This chapter tests the argument using statistical evidence. Specifically, the theoretical hypotheses to be tested are:

1. H1: States led by revolutionary governments are more likely to instigate militarized interstate disputes than comparable non-revolutionary governments.

2. H2: The difference between revolutionary and non-revolutionary governments, in terms of their propensity to instigate international conflict, will be greater in petrostates than in non-petrostates.

To preview the findings, the empirical evidence supports both hypotheses. Among non-petrostates, revolutionary governments are about 50 percent more likely to instigate militarized interstate disputes (MIDs) than non-revolutionary ones. And among petrostates, the difference is even more dramatic: petro-revolutionary governments are about 250 percent more likely to instigate MIDs than non-revolutionary ones.