As captured by neorealist theory, military power became increasingly relative through into the twentieth century, leading to a concentration of power within and between states—and enabling the buildup of huge colonial empires hardly a century ago. Yet since 1945, due to the overproportional effectivity gained by weaker and in particular nonstate actors it has become less relative, leading to a dispersion of power—resulting in an often violent decolonization, the problems US and North Atlantic Treaty Organization forces have faced in Iraq and Afghanistan in dealing with comparatively small insurgencies and a growing number of failing states. Military power has a selective function: the more relative it is, the more it restricts patterns of conflict as well as the number and nature of actors relevant to international and domestic security. Today, it is because military power is becoming less relative that security policy has to adapt to increasingly asymmetric challenges.