The demise of Moammar Gaddafi — and the liberation of the Libyan people from more than 40 years of tyranny — demonstrates the powerful forces for change that are reshaping the Arab world. It also highlights the unique and irreplaceable value of U.S. leadership of strong alliances.

President Obama has made strengthening our security alliances in Europe and Asia a cornerstone of America’s engagement with the world. These alliances provide unique benefits to U.S. security: shared threat assessments, reliable habits of cooperation, the ability to take military action quickly and seamlessly, real burden-sharing for the American taxpayer, and democratic values that we hold in common. They reflect the persistent work of presidents of both parties since the end of World War II. No other nation possesses anything like the U.S. alliance system.

In Libya, the investment the United States has made in revitalizing NATO has paid off in multiple ways:

First, NATO acted with dispatch to achieve a clearly defined mission to protect civilians. This was the fastest formation of a NATO operation in history. After the United States provided the lead in the early days, NATO quickly took over command and control of the entire military effort, protecting Libyan civilians as the Transitional National Council organized, grew in strength and ultimately drove Gaddafi from power.

Second, the speed and effectiveness of the operation would not have been possible if we had had to rely on an ad hoc coalition of the willing. At the outset, NATO members and Arab partners explicitly requested that NATO take over command and control to ensure full coordination among the 18 countries involved. Significantly, the United Arab Emirates and Qatar were full partners in the effort — a testament to NATO’s relationships with nonmember countries throughout the world. The ability to rapidly integrate such countries within NATO’s command-and-control architecture stems from the fact that NATO has the only standing multinational military command structure in the world.

Third, the operation demonstrated the value of maintaining highly capable militaries that plan, train and equip together. NATO planes flew more than 26,000 sorties and nearly 10,000 strike sorties. The United States provided the bulk of the military muscle in the early days to halt Gaddafi’s advances and then played an indispensable supporting role with its unique assets, flying three-quarters of the surveillance and aerial refueling missions. But our allies also stepped up. Overall, U.S. forces flew just more than 10 percent of the strike missions. Perhaps most impressive as a sign of collective strength, countries other than the United States, the United Kingdom and France flew nearly half of all sorties. Belgium, Canada, Denmark, Italy and Norway fully participated in the civilian-protection mission. The Netherlands, Spain, Sweden, Turkey and others found additional ways to contribute.

Fourth, this operation shows that sharing the burden is more than a slogan — it means sharing the costs. Our total contribution to the nearly eight months of operations in Libya will be approximately $1.2 billion — a fraction of the overall international contribution to Libya — and less than a week’s worth of the cost of operations in Afghanistan or Iraq.

In this effort, the U.S. leadership role remained decisive. Last March, President Obama directed that we shape a robust U.N. Security Council resolution with teeth — enabling international action to hold Gaddafi to account. He insisted that we precisely define our role so that U.S. forces would do what no other nation could do in shaping the battlefield in the campaign’s early days. And he intervened at critical junctures to increase the pressure on Gaddafi and support the Libyan people — adding armed Predators to the effort in June; increasing intelligence and targeting resources over the summer; and rallying other nations to join us in recognizing a new Libyan government in July. This approach succeeded in meeting our objectives and led to a division of labor that enabled others to contribute based on their distinctive capabilities and interests.

As we take stock of NATO’s strengths, we will also focus on how our alliance can be more effective in the future. We know that allies need more advanced intelligence, surveillance and reconnaissance capabilities. They face shortages in helicopters and transport aircraft. They need to make greater investments in the precision munitions and unmanned systems that are critical on today’s battlefields and will be even more important in the future. As President Obama prepares to host the next NATO summit in Chicago in May, he is asking the alliance to ensure that it has cutting-edge capabilities.

Libya is liberated today because NATO’s unmatched might was joined by an indigenous movement for change led by the Libyan people, who broke the back of the regime.

In the days ahead, Libya will face many challenges as it works to heal the wounds created by decades of Gaddafi’s rule — from standing up a new government to securing and destroying dangerous weapons to assisting thousands of wounded and displaced citizens. Although NATO’s military mission is ending, the United States and its NATO allies will continue to work to support the new Libya.

This underscores a basic fact: From the Atlantic to the Pacific, America’s strong alliances and partnerships are an enduring source of our national strength and global leadership — helping underwrite our security, enabling our prosperity, and promoting our values.

The writer is national security adviser to President Obama.