Nothing has been more dispiriting in the nearly two decades since the end of the Cold War than the ineptitude and lack of purpose in the conduct of American foreign policy. As Casey Stengel said, “Can’t anybody here play this game?” If only it were only a game.

I signed on with Mayor Giuliani to help him run for president because, alone of all the candidates of either party, he can fill America’s — and the world’s — most profound and urgent need: to make the international state system work in an effective, principled, and cooperatively businesslike way. Rudy Giuliani is the only candidate with the tested national and international executive experience needed to turn this calamitous international situation around.

In the 1980s when I was in the State Department, Mr. Giuliani was at the Department of Justice. He was at work to overcome difficult legal and political obstacles in allied countries so that President Reagan’s policy to turn back the Soviet nuclear missile threat to Western Europe could go forward.

In the 1990s when I was working with the United Nation’s Secretary General at the organization’s headquarters I experienced New York City first-hand, both before — foul, fearful, and demoralized — and after — revitalized, safe, and humming — the election of Mayor Giuliani. There is a unique international role played by the leader of New York since New York is considered the world’s capital city.

In today’s daunting context, Mr. Giuliani has the three-dimensional talent the American presidency demands.

First, he has the core attributes of brains, energy, decisiveness, and vision. He also has a unique ability to use everyday language to explain a problem, set forth the way to a solution, and bring people along in a cooperative effort.

Second, Mr. Giuliani has a genius for non-ideological problem solving. He has achieved practical results time after time because he won’t be categorized or captured by someone else’s dogma.

Third, Mr. Giuliani has a principled pragmatism. He’s done the homework and knows the ins and outs of all the issues. He’s worked out his position on the various presidential matters. He won’t budge his position on them without anything other than sound reasoning, hard facts, and caring attention to the human and spiritual consequences involved. He has a people-first approach.

In the years since September 11, he has traveled to countries in every part of the world and talked with both statesmen and people on the street. During the war years in Vietnam, the American army was on the skids with new leadership, but came back to secure victory in the final stages of the Cold War.

The dangers today are greater than ever: from individual terrorists bent on mass slaughter to Iran’s blatant, radical Islamist drive for nuclear weapons. At the Citadel earlier this year Mr. Giuliani declared his determination to put our military establishment on the right road. None of his presidential political rivals can match his readiness to reform our dysfunctional intelligence system.

As a former Career Minister of the Foreign Service of the United States, I am particularly concerned with the condition of American diplomacy. It has long been associated with compromise and accommodation. Too often it practiced as though that were its sole purpose. But America now must have a stronger and more active diplomacy. Above all we need to understand that diplomacy, to be effective, must be conducted in tandem with, not as an alternative to, our economic, cultural, and military power resources.

From my first contact with Rudy Giuliani I recognized that he possesses the greatest interest and insight of any major figure I have known since George Shultz about America’s foreign service career. As president, Mr. Giuliani would give the State Department and Foreign Service the attention and leadership it sorely needs.

There are tough decisions that must be taken by the next president. On the foundation of those hard choices, an unprecedented bright and peaceful future is close at hand. As Mr. Giuliani has said, “Now is a golden moment of economic opportunity for the world.” His energy, optimism, and long record of getting results can make it a reality.

Mr. Hill is the chief foreign policy adviser for Mr. Giuliani’s presidential campaign.