In the Obama White House, the mantra of “leading from behind” was so deeply embedded that America’s allies were often left confused and disoriented when it came to U.S. foreign policy.

President Barack Obama’s 2015 national security strategy was a curious mishmash of lofty idealism and outreach to dictatorial regimes such as Iran and Cuba, combined with a refusal to even acknowledge that an ideological war existed against Islamists.

Obama’s national security strategy listed climate change as a “top strategic risk to our interests” alongside use of weapons of mass destruction, while the threat posed by ISIS and al-Qaeda was simply dubbed “violent extremism.” Just as Obama himself began his two-term presidency with an apology tour across the world, his strategy warned that America’s own values had been under threat in the post-9/11 era in the war on terror.

The new national security strategy released early Monday by President Donald Trump’s White House sets a very different, distinctly unapologetic tone. It takes a clear-cut view of the immense challenges faced by the United States from an array of actors, from Russia, China, and North Korea to transnational, largely Islamist terror networks. In addition, the strategy emphatically rules out the idea of extending the hand of friendship to rogue regimes such as Iran.

The projection of American leadership is front and center in the new strategy. The document contains a strong rejection of the idea that the United States should share global leadership with Moscow and Beijng in a supposedly multipolar world:

The United States will respond to the growing political, economic, and military competitions we face around the world. China and Russia challenge American power, influence, and interests, attempting to erode American security and prosperity. They are determined to make economies less free and less fair, to grow their militaries, and to control information and data to repress their societies and expand their influence. These competitions require the United States to rethink the policies of the past two decades—policies based on the assumption that engagement with rivals and their inclusion in international institutions and global commerce would turn them into benign actors and trustworthy partners. For the most part, this premise turned outlateral to be false.

Trump’s national security strategy, which runs to 70 pages (in contrast to 2015’s 29 pages), outlines four pillars for advancing and defending America’s interests on the world stage: protecting the American people, the homeland, and the American way of life; promoting American prosperity; preserving peace through strength; and advancing American influence.

At the core of the new strategy is an emphasis on controlling America’s borders, rebuilding America’s military, and competing and leading in international organizations, including NATO and the United Nations, while pressing to make them more accountable and effective.

As the new strategy makes clear, America’s enemies should be under no illusions regarding U.S. resolve:

We must convince adversaries that we can and will defeat them—not just punish them if they attack the United States. We must ensure the ability to deter potential enemies by denial—convincing them that they cannot accomplish objectives through the use of force or other forms of aggression. We need our allies to do the same.

The document is a bold reassertion of American leadership and a refusal to bow to the siren calls of isolationism. It is a robust defense of the principles of national sovereignty and self-determination, as well as a recognition that the United States can best lead on the world stage by upholding its own sovereignty and that of its allies.

The document also includes powerful support for religious freedom, an important message to send both at home and abroad, as well as a welcome call to rethink foreign aid, by basing foreign assistance on free-market principles and private investment.

The 2017 national security strategy should reassure America’s friends and allies that the United States is firmly committed to leading the free world. At the same time, it should serve as a stark warning to America’s adversaries and strategic competitors that the U.S. will renew its military might, reject failed strategies of engagement, and use its resources to challenge and, where necessary, defeat those who threaten the security of the American people.