In a young century, opportunities for America abound, but risks to our security remain. This new National Security Strategy positions the United States to safeguard our national interests through strong and sustainable leadership. It sets out the principles and priorities to guide the use of American power and influence in the world. It advances a model of American leadership rooted in the foundation of America's economic and technological strength and the values of the American people. It redoubles our commit-ment to allies and partners and welcomes the constructive contributions of responsible rising powers. It signals our resolve and readiness to deter and, if necessary, defeat potential adversaries. It affirms America's leadership role within a rules-based international order that works best through empowered citizens, responsible states, and effective regional and international organizations. And it serves as a compass for how this Administration, in partnership with the Congress, will lead the world through a shifting security landscape toward a more durable peace and a new prosperity. This strategy builds on the progress of the last 6years, in which our active leadership has helped the world recover from a global economic crisis and respond to an array of emerging challenges. Our progress includes strengthening an unrivaled alliance system, underpinned by our enduring partner-ship with Europe, while investing in nascent multilateral forums like the G-20 and East Asia Summit. We brought most of our troops home after more than a decade of honorable service in two wars while adapting our counterterrorism strategy for an evolving terrorist threat. We led a multinational coalition to support the Afghan government to take responsibility for the security of their country, while supporting Afghanistan's first peaceful, democratic transition of power. The United States led the international response to natural disasters, including the earthquake in Haiti, the earthquake and tsunami in Japan, and the typhoon in the Philippines to save lives, prevent greater damage, and support efforts to rebuild. We led international efforts to stop the proliferation of nuclear weapons, including by building an unprecedented international sanctions regime to hold Iran responsible for failing to meet its international obligations, while pursuing a diplomatic effort that has already stopped the progress of Iran's nuclear program and rolled it back in key respects. We are rebalancing toward Asia and the Pacific while seeking new opportunities for partnership and investment in Africa and the Americas, where we have spurred greater agriculture and energy-related investments than ever before. And at home and abroad, we are taking concerted action to confront the dangers posed by climate change and to strengthen our energy security. Still, there is no shortage of challenges that demand continued American leadership. The potential proliferation of weapons of mass destruction, particularly nuclear weapons, poses a grave risk. Even as we have decimated al-Qa'ida's core leadership, more diffuse networks of al-Qa'ida, ISIL, and affiliated groups threaten U.S. citizens, interests, allies, and partners. Violent extremists exploit upheaval across the MiddleEast and North Africa. Fragile and conflict-affected states incubate and spawn infectious disease, illicit weapons and drug smugglers, and destabilizing refugee flows. Too often, failures in governance and endemic corruption hold back the potential of rising regions. The danger of disruptive and even destructive cyber-attack is growing, and the risk of another global economic slowdown remains. The international community's ability to respond effectively to these and other risks is helped or hindered by the behaviors of major powers. Where progress has been most profound, it is due to the steadfastness of our allies and the cooperation of other emerging powers."