If one is searching for historical analogies – of course, they are never exact – this moment, in my judgment, most resembles 1940. In that year the world looked very bleak. The German blitzkrieg across Europe reached its height when France fell and goose-stepping Nazi troops paraded down the Champs Elysee.

Great Britain was surrounded and alone. Bombing of London was a nightly occurrence; the Underground served as refuge for wary and frightened residents. The United States was sympathetic, but technically neutral. Lend-Lease offered supplies and politicians offered words of support. However, there were more words than assistance.

American Firsters met in Madison Square Garden, with Charles Lindberg urging Americans to stay out of the war. While sympathy was overwhelmingly with our British allies, there were active German bund movements on American soil and publications that suggested fascism was the wave of the future.

Democracies not only lost in battle to the Wehrmacht, they seemingly lost their confidence. It was a year of frightening headlines. German submarines destroyed American tankers crossing the Atlantic. The Hitler-Stalin alliance was still in effect, giving Hitler confidence that he did not have to worry about his eastern front. And fascism had not yet been subject to the searing critique found in the years ahead. In fact, Mussolini, at this point, was admired by many.

The Hitlerian plan for the extermination of Jews set out in “Mein Kampf” was well underway by 1940. Kristallnacht had already occurred. Despite what most Western leaders knew about the Holocaust, they chose to deny the reality or believed the claims of killing fields were exaggerated. After all, what could we do about it in any case?

Flash ahead to 2006. A relentless enemy of the West and of democracy has emerged on the world stage. Its philosophical underpinnings are totalistic, not unlike the fascism of yesteryear.

To the surprise of many, this radical Islamic belief has captured the imagination of some incalculable segment of the Muslim population. They read the passages of the Koran selectively searching for those words that justify violence and martyrdom.

The dream of Osama bin Laden is Hitler’s dream, but instead of an Aryan empire across the globe, Muslim extremists believe in caliphates across the globe spreading the faith and in the process destroying liberal democracies.

Rather than stand up to this challenge, many European government attempt to appease and mollify the extremists in their midst. Even when shahadists say we want to kill the infidels, many Europeans choose not to believe their words. They are living a liberal fantasy that some accommodation can be reached. The ghost of Neville Chamberlain lives.

America is not immune from this mind set. For Democrats, President Bush is a warmonger intent on finding enemies in remote places. Mr. Bush, himself, is equivocal about the war effort he pursued after September 11, as the initial pull back from Fallujah would suggest.

So confused is the Western mind that it cannot stand forthrightly for its own principles, as President Clinton’s apology for the Danish cartoons unabashedly indicates. Recognizing this weakness and the apparent confusion, radical Islam has come to the conclusion that this is its 1940, the moment of final solution. Egypt is teetering on the precipice of radicalism; Pakistan could fall if Musharaf is assassinated. Hamas is in the grip of fanaticism, and Mahmoud Ahmadinejad speaks of a romantic attachment to martyrdom. The armies of Islam are on the march.

Now for a moment of sobriety amid this lugubrious scenario. At the point of no return, Churchill summoned the will to resist Hitler. The United States entered the war in Europe after the attack on Pearl Harbor. Most significantly, our energies were mobilized to fight this war for survival.

We are back in 1940. Our backs are against the wall and we must summon the strength to defend our civilization. There isn’t any turning away; nor can we rationalize our way out of this battle. The other side is relentless; it believes Allah is on its side. If we dither, we lose; if we recognize the danger and marshal the spirit to respond, we will prevail as we did in World War II.

Mr. London is the president of Hudson Institute and professor emeritus of New York University. He is the author of “Decade of Denial” (Lanham, Maryland: Lexington Books, 2001).