Military objectives often can be pursued using a number of different approaches: airpower versus ground forces, larger munitions versus smaller ones, more-or less-restrictive rules of engagement. Military effectiveness often favors the immediate application of overwhelming force, but militaries and their civilian overseers often opt for more-restrained approaches. Understanding how and why policymakers have chosen to impose these restraints in the past and how and wiry they are likely to do so in the future is critical to understanding how states will conduct future wars. This report identifies four key trends likely to shape the future exercise of restraint in warfare: the spread of lawfare (or use of law as a weapon of war), the widespread distribution of imagery of U.S. military operations, the increasing effectiveness of false accusations, and the increasing public concern for civilian casualties. These trends are assessed for how likely they are to affect both conflict between states and between states and nonstate actors, in addition to how the effects of these trends might differ for different types of states. Overall, these trends appear likely to further increase the incentives of decisionmakers in liberal democratic states to avoid civilian casualties in conflicts against weaker adversaries and to support investments in capabilities to make this possible. Other states that are more autocratic are not likely to be similarly constrained, and policymakers in democratic states will need to adapt to this asymmetry. Between highly capable state actors, conflict is less likely to occur but could involve very different incentives if operational considerations prompt a sharp reduction in the degree of restraint exercised beyond each state's legal obligations and the public shows a greater tolerance of heightened levels of military casualties and collateral damage to civilians. This report also provides specific recommendations for U.S. policymakers to begin to adapt to these anticipated trends. Book jacket.