On Sept. 11, 2001, America entered a new world war. Our nation had been violated by the barbarism of a new dark age. The Free World had been shaken to its core. In the days and weeks immediately following the horrific attacks on our homeland, it seemed there was no telecast or broadcast, no newspaper or magazine that did not mention the name of Winston Churchill. The gatekeepers of information looked for guidance, inspiration and hope to the memory of one man who rallied a nation in peril to battle the forces that threatened to strike it down.

Rarely have a man and a moment been so perfectly matched than in May 1940, when Churchill became prime minister of Great Britain. His were the most dangerous of times in which the fate of the world hung in the balance. His uncertain days seemed to be waiting for a certain kind of leader, a leader with an unmatched spirit of courage and conviction.

With unwavering assurance, he believed destiny had prepared him for that moment in history. As history looks back, it is assured, as well, for without his leadership, the fate of his nation and the world would have taken a markedly different course. As world events continue to unfold, it is evident that the spirit of Churchill is still the prime requirement of this moment.

In her new book, “The Spirit of Churchill,” author Deborah Brezina heralds a stirring call to this present generation to reclaim the noble heritage of those who preserved our freedom. Brezina takes the reader through the major events of World War II and presents a leader who left no room for compromise in the defense of liberty – a leader who understood he had to take a stand, regardless of the consequences.

“The Spirit of Churchill” challenges and inspires by the heroic example of a man who never gave up, who only considered victory in the face of defeat and who had indomitable determination to stand alone, if that’s what it took, for what he believed was right. The book stresses a vital truth: What one believes matters. In 1940, it mattered to the whole world. In the 21st century, it still does.

On March 3, 2004, in the rush hour of a normal workweek, bombs ripped through four commuter trains in Madrid. Just a week before its national elections, Spain was hit hard by Islamic terrorists. The death toll was 132 innocent men, women and children. Many believe in the aftermath that terrorists altered an election and set a different course for a nation.

In the wake of the al-Qaida bombings in Madrid, the comprehensive war against global terrorism by democratic nations seemed in jeopardy. This was not Europe’s first experience with appeasement. Italy’s Corriere della Sera warned: “The spirit of Munich is again blowing across Europe.”

On June 7, 2005, in the heart of London, the worst strike of terror on British soil since World War II shattered a summer morning. Within hours, the resolve of the British people was evident. A phrase used countless times during the blitz of six decades before was heard again: “London can take it!”

Dazed and bloodied Britons who survived blasts on three London subway trains and one double-decker bus seemed to speak with a single voice: “If that’s all they can do to us, we will make it!” The British nation took it in stride and carried on: “We won’t give in to terror – no matter the cost!” The world again witnessed the spirit of Churchill.

Because the long tradition of democracy runs deep in the history and psyche of Great Britain, the question becomes: Does Britain have the spirit of Churchill or did Churchill have the spirit of Britain? At the celebration of Churchill’s 80th birthday, this question was posed.

In characteristic wit and wisdom, the lion of England aptly replied: “It was the nation who had the lion’s heart. I had the luck to be called upon to give the roar.”

Churchill forged for his nation and the Western world the understanding of why we fight. He lived in view of his mortality. In time of terror, his indomitable spirit lives on in immortality.

As the civilized world stands once more against a hateful enemy, freedom-loving men and women have need of principled leaders and steady statesmen. As never before, statesmen of strong fiber are not only essential, they are indispensable if the cause of peace, freedom and civilization is to prevail.

The Free World has a choice either to learn or not learn the lessons of history. Each choice comes with consequences. In the days and years to come, the world will choose the spirit of Munich or the spirit of Churchill. Let’s make sure the spirit of Churchill prevails.

Mr. Kemp is founder and chairman of Kemp Partners.