Violent conflicts although abated somewhat in the 21^st century, tragedies of war are prevalent in many regions of the world. Conflicts are of two types: those involving citizens of one nation (civil wars) and those involving two or more nations (interstate wars). In this study I raise the following questions: what are the motivations for state governments to engage in mass killing at some stage in the conflicts? Why do states engage in armed conflict against one another?

The study is comprised of two essays.

The first essay, "An Economic Approach to Mass Killing", inquires about the conditions that must be met for a civil war to evolve into mass killing. A game-theoretic framework is used. The theoretical model is tested using panel data on one-sided violence against civilians from the Uppsala Conflict Data Program (UCDP) over the period 1989-2005. Three hypotheses are investigated employing probit-random-effects and random-effects models. The results show that the likelihood of mass killing depends on the type of natural-resources endowment in a country in conflict. The existence of diamond and oil onshore increases the probability of occurrence of mass killing episodes during a civil war; whereas drugs production has no effect on the likelihood of violence. The results also show that the size of a country's military expenditure increases the likelihood of mass killing. Country's ethnic fractionalization seems to have no significant effect on the violence perpetrated against civilians.

The second essay, "A Game-Theoretic Approach to War", utilizes a bargaining framework to test for the likelihood of war onset and the factors that contribute to large numbers of battle deaths. Data on interstate disputes were obtained from the Correlates of War project for the period 1816-2001. A heteroskedastic-probit model and a Feasible Generalized Least Squares model are employed. The estimation results confirm the essential implications of the theoretical model. They show that an oil-producing country is more likely to be militarily attacked, and conflicts involving oil-producing and drugs-producing defenders result in more battle deaths. The cost of a military conflict has a significant positive effect on the likelihood of interstate wars.