This week marks a significant anniversary, one that carries with it some crucial lessons as the West confronts the mounting danger posed by the Muslim jihadis of the Islamic State of Iraq and Syria. It was 75 years ago, at 4:45 a.m. on September 1, 1939, that a German warship fired on Polish troops stationed at the Westerplatte Fort in the port city of Danzig, signifying the start of World War II. It was a cataclysm that would engulf the globe, killing more than 50 million human beings while permanently altering the international order. According to Britain’s wartime prime minister, Winston Churchill, it was one that should never have had to been fought.

In the preface to “The Gathering Storm,” the first of his magisterial six-volume account of World War II, Churchill relates the following story: “One day, President Roosevelt told me that he was asking publicly for suggestions about what the war should be called. I said at once, ‘The Unnecessary War.’ There never was a war more easy to stop than that which has just wrecked what was left of the world from the previous struggle.”

Churchill said that he would proceed to explain “How the English-speaking peoples through their unwisdom, carelessness, and good nature allowed the wicked to rearm.” Through their dithering, the Western powers had allowed Germany to re-equip itself after its defeat in World War I, a process that could have been stopped at any time through force and determination.

When the German chancellor, Adolf Hitler, launched his expansionist enterprise in March 1936 by seizing the Rhineland and remilitarizing it in violation of the Treaty of Versailles, which had ended the previous global conflict, nothing was done to stop him. From there, the road to the March 1938 Anschluss in Austria, followed by the dismemberment of Czechoslovakia and on to full-scale war, was short and inevitable.

After such a calamitous series of events, one would have assumed that the international community would have learned its lesson. By allowing Nazism to fester and grow, and by sitting on the sidelines as it consolidated its power and pushed beyond international borders, the Western world had made a nearly fatal mistake.

And yet, it appears that the same shortsightedness, lack of purpose and sense of urgency in the face of the ISIS threat are once again threatening to breed a disaster of epic proportions. Nowhere is this negligence on greater display than in Washington itself, where President Obama has spent more time pondering which golf club to use on the green than how much force to deploy in Iraq and Syria.

In the January 27 number of the New Yorker magazine, issued shortly after ISIS had captured the Iraqi town of Falluja but 43 miles west of Baghdad, Mr. Obama compared the terrorist group to a junior varsity basketball team masquerading as professional NBA team. “The analogy we use around here sometimes, and I think is accurate, is if a JV team puts on Lakers uniforms that doesn’t make them Kobe Bryant,” the President said.

Then he added: “I think there is a distinction between the capacity and reach of a bin-Laden and a network that is actively planning major terrorist plots against the homeland versus jihadis who are engaged in various local power struggles and disputes, often sectarian.” While the White House subsequently tried to “clarify” Mr. Obama’s remarks, it was clear that he was belittling the aptitude and capability of ISIS.

In subsequent months, as ISIS proceeded to capture Mosul, Iraq’s second largest city, as well as large swathes of neighboring Syria, it quickly became clear just how misguided the commander-in-chief’s analysis had been. This led columnist Jonah Goldberg to note that “that same junior varsity team controls more territory than any terrorist organization in history, has some 5,000 battle-hardened jihadists with Western passports, hundreds of millions of dollars at its disposal and is earning millions more every day by selling oil on the black market.”

Despite the organization’s rapid growth, and the clear and present danger that it poses to the West, Mr. Obama has yet to figure out what to do. As he acknowledged in remarks to reporters last Thursday, “I don’t want to put the cart before the horse, we don’t have a strategy yet.”

Just what exactly is Obama waiting for? Today’s jihadis pose a threat to Western civilization no less ominous than that of last century’s Nazis. With their totalitarian ideology and ruthless brutality, they are bent on global domination. If allowed to continue gaining steam, as the Nazis were able to do throughout the 1930s, groups such as ISIS, al-Qaida, Hamas, and other Islamic jihadis will be far more difficult to stop.

While Prime Minister Cameron on Friday came out with a forceful warning regarding ISIS and growing Islamic extremism, Washington has yet to show any signs that it will heed his counsel. There is still time to stop ISIS and other groups, before they expand still further into Lebanon, Jordan and elsewhere. But the longer Obama fiddles, the more the Middle East will burn.

So as we recall the events of 75 years ago this week, it is worth remembering Churchill’s unsettling conclusion that “the tragedy of the Second World War could have been prevented,” but “the malice of the wicked was reinforced by the weakness of the virtuous.” It was the act of waiting too long which led to World War II against the Nazis. And the longer the West waits now, the sooner it will find itself having to wage World War III against the jihadis.

Adapted from the Jerusalem Post.