“All's fair in love and war,” so the saying goes. But, of course, we know that it's not true. For we commonly judge and sometimes punish individuals, in the arena of love, for infidelity, deceit, and crimes of passion; and we commonly judge and sometimes punish individuals, in the arena of combat, for acts of aggression, rape and pillage in war, and crimes against humanity. The intense pressure of competition, in both affairs of the heart and the crucible of war, can help explain why unfair, even inhumane, behavior is common, but it does not excuse it.
Several technological innovations and political developments are changing the nature of warfare today in ways that pose complex challenges to the traditional standards that we use, under the influence of international law and just war doctrine, to judge governments' and individuals' actions in war. New technologies – including the use of drones, precision-guided weapons, cyber weapons, and autonomous robots – have led both to optimism about the possibility of reducing collateral damage in war and to concerns about whether some states find it too easy to use force today. New technologies also have been developed, however, that can provide early warning of civil conflict and promote more effective peacekeeping operations. On the political front, the growth of terrorism by nonstate actors, the spread of weapons of mass destruction, and changing doctrines in the United Nations about the responsibility to protect civilians pose new questions about the appropriate legal rules and ethical norms governing decisions to use military force. Professional military lawyers play an increasingly important role in reviewing targeting policies and rules of engagement, at least in the United States, to ensure that military plans and operations are compliant with the laws of armed conflict. War crimes tribunals have grown in use, but raise new questions about whether they encourage ruthless leaders to fight to the finish rather than accept resignation and exile. New knowledge about post-conflict medical system failures raises questions about both the best practices to end wars and sustain peace accords and about whether political leaders systematically underestimate the costs of going to war before they make decisions about military interventions.