As we assess a complex security environment, our historical experience provides useful context and guideposts to understanding the present, even when security threats are harder to define and address, as in the case of cyber attacks. U.S. forces are also held to standards increasingly difficult to guarantee; the prospect of even minimal casualties to our own forces or to civilians (however unintentional) or unintended environmental damage now colors every decision in the age of the 24- hour news cycle. On balance, traditional military security concerns often seem less paramount. Absent a clear and present danger, humanitarian considerations, environmental issues, and resource impacts and scarcities compete strongly with military factors in policy deliberations. In the meantime, nonstate actors are increasing their power and influence to bring about policy changes across a wide spectrum of issues, many of which directly affect the ability of U.S. military forces to carry out their missions. In the last generation, we often saw the face of the future reflected in the bitter divisions of the past, in failed states, in emerging democracies, and in nations stuck in transition between authoritarian and democratic systems. A persistently uncertain and unstable international security environment places a premium on U.S. leadership. As the only remaining global power and as a coalition leader in organizations like NATO, the United States is uniquely positioned to influence world affairs in ways that benefit not only it, but also the international community as a whole. The prudent use of American military power, in concert with the economic, political, and diplomatic instruments of national power, remains central to attempts to shape the international environment and encourage peace and stability wherever important U.S. interests are at stake. As George Kennan put it, “We have learned not to recoil from the struggle for power as something shocking or abnormal. It is the medium in which we work . . . and we will not improve our performance by trying to dress it up as something else.”