It’s neither a faculty lounge problem nor a war game, of course. An estimated four million refugees from Syria, Iraq, Libya and Yemen — as well as Afghanistan — are fleeing the conflicts in their nations for the possibility of a more peaceful home in Europe. As is often said, it is the largest refugee crisis Europe has endured since World War II.

However, if you analyze the crisis in war game terms, it becomes clearer why and how Europe is losing and will be defeated.

There are three sides in our war game scenario and it’s possible for more than one to “win.” On one side are the 28 European Union nations, many of which are members of NATO. They are not-quite-governed by the not-quite-sovereign European Union.

They face a tidal wave of refugees that threatens to radically change their demographic identity. It is something less than an invasion but much more than what peace can accommodate. It is, in short, a significant threat to their national security and their economies.

The refugees are flowing to Europe at the rate of roughly 200,000 per month. The EU nation’s reactions have been erratic and confused.

In August, German Chancellor Angela Merkel welcomed them. In September, her government said that any Syrian who made it to Germany could claim asylum there. That inevitably attracted a growing flood of tens of thousands to cross Greece, Italy and other nations to reach Germany. And then the Germans stopped rail traffic bringing more refugees. Hungary has tried to seal its borders with Croatia and Romania, trapping many in limbo.

The Schengen Agreement, which permits passport-free travel among EU nations, is already a dead letter. Entering Hungary from Croatia last week, my wife and I found Hungarian passport control to be a stern presence. Flying from Budapest to Frankfurt on our trip home, we had to show our passports four times, including upon exiting the aircraft.

The best the EU has done so far is to agree to a plan to settle 120,000 refugees across the EU’s 28 member nations, but that agreement came at the cost of overriding four member governments’ objections, which is almost unheard of in EU history. That agreement deals with less than one month’s flow of refugees. It doesn’t attempt to deal with the almost 800,000 refugees expected this year in Germany alone.

The second side in our war game is comprised of Bashar Assad’s Syrian dictatorship and its Russian and Iranian allies. They latter two are determined to keep their terrorist ally in power at any cost. They weren’t powerful enough (or sufficiently Machiavellian) to order up the refugee crisis but they — especially Russia — are eager to gain from it by conducting what is, in effect, a proxy war against European stability and unity.

Russia is also gaining by deploying aircraft, tanks, drones and troops to Syria, cementing its control over the western part of that nation. The obvious threat of those forces to Israel has already brought Israeli Prime Minister Netanyahu to Moscow to seek Russian President Vladimir Putin’s assurances that his forces will not be used against his nation. Mr. Netanyahu understands how little faith he can place in whatever Mr. Putin may have told him.

The third side in the war game is comprised of the various terrorist groups — including ISIS and the al-Nusra front to name just two — who stand to gain ground by taking what the refugees leave. Thanks to President Obama’s ill-advised Libyan intervention, the Gadhafi government — which was no threat to us and relatively stable — fell and has been replaced by several quasi-governments of various terrorist brands. They, too, benefit from the refugee crisis by consolidating their control over various parts of Libya.

In every war game the defenders have must choose between defending their interests by some combination of diplomatic, economic and military means or accepting some version of defeat. They have to seek to end or defeat the threat.

What is entirely absent from the European debate is the idea of taking steps to stop the human tidal wave by stabilizing the nations from which the refugees flow. That might even cause many to return to their home countries. Europe can’t debate those steps, far less undertake them, because their nations are incapable doing so.

The European nations, including almost all NATO members, chose to rely on America’s protection and to refuse to invest in their own defenses, resulting in de facto unilateral disarmament. Their military forces, having shot their last bolt in Libya, cannot project any level of power remotely capable of ending any of the conflicts in the Middle East and Afghanistan.

That ends the game with Europe the big loser. It is left with the certainty of having to absorb millions of refugees and whatever burden they place on their nations’ security and economies.

The EU is now irrelevant to its member nations’ security. By surrendering their sovereignty to the EU, they failed to perform the sovereign’s first duty: to protect their peoples against the depredations of war, be it kinetic or demographic.

• Jed Babbin served as a deputy undersecretary of defense in the George H.W. Bush administration. He is a senior fellow of the London Center for Policy Research and the author of five books including “In the Words of Our Enemies.”