In the latter half of the twentieth century, lasting memories of two world wars and astonishment over the power of nuclear weapons left both policymakers and scholars of war largely preoccupied with the possibility of a catastrophic World War III. Instead, however, the face of war since 1945 has been that of regionally limited small wars and insurgencies fought with conventional weapons. Many of these conflicts began as armed rebellions against colonial regimes, but often later evolved into armed conflicts between and among various subgroups seeking control of state government. Such conflicts have usually been asymmetrical, with the party holding the reins of state power using aircraft, artillery, and armored vehicles, while those fighting against the regime have been limited to weapons that individuals can carry, such as automatic rifles, mortars, rocket-propelled grenade launchers, and improvised weapons of various sorts. The asymmetries have also typically gone deeper, with the fighters on the former side wearing uniforms and those on the latter often not; those on the former side making use of fortified bases and those on the latter side protecting themselves by blending in with the civilian population. Further, there have frequently been asymmetries in how each side has fought, with the militarily weaker side relying on stealth tactics, deception, and attacks against nonmilitary targets of more general public value, including direct attacks on people protected as noncombatants under the laws of war. The particular range of tactics classified as terrorism begins at this point, with the specific, direct, and intentional targeting of noncombatants. Such attacks not only have been the means of choice for transnational nonstate actors, including al-Qaeda and the self-styled Islamic State, but have also been used to considerable effect in local civil wars.