In 1942, Winston Churchill said that Italy was the “soft underbelly” of Europe and directed Allied invasion efforts there. Today, we are seeing flickers of a similar strategy from the Islamic State.

Following the decapitation of 21 Egyptian Coptic Christians by radical Islamists professing an allegiance to the Islamic State, the Italian government has begun ramping up efforts to defend its territory from attack. How realistic is this threat? And what should Italy do?

First, we should listen to what the Islamic State has to say : Last year, the group’s propaganda magazine Dabiq featured a cover story headlined “Reflections on the Final Crusade,” which was illustrated with an image of a black jihadist flag flying over St. Peter’s Square. “We will conquer your Rome, break your crosses, and enslave your women,” a senior leader of the group was quoted as saying.

“If we do not reach that time, then our children and grandchildren will reach it, and they will sell your sons as slaves at the slave market.” Elsewhere, the magazine exhorted, “Every Muslim should get out of his house, find a crusader and kill him. . . . And the Islamic State will remain until its banner flies over Rome.”

Hyperbolic? Of course. Literally possible? Not in the least. But should Europeans take these words into account as they think about the possibility of attacks on their homeland? You bet.

As Graeme Wood pointed out in his smart, historically grounded piece in the Atlantic this month, “What ISIS Really Wants,” there is an underlying medieval impetus to the Islamic State’s rhetoric and actions.

Beheadings of innocents, burnings of prisoners, crucifixions, the enslavement and sale of women and children, the literal sacking of cities — all of these connote a desire to play on the international stage as though the Crusades were still occurring. Thus we come to the importance of Rome, perhaps the most potent symbol of all that the Islamic State hates.

The Islamic State does not have the capability to launch a conventional attack on Italy, but it has two potential routes into the country by sea. It could infiltrate the boatloads of illegal migrants who sail the short distance from Libya to Italy’s southern coast and islands. Or it could use small craft, much as smugglers and drug runners do on the Adriatic, to cross the southern Mediterranean. Both methods would be easier than entering over land through Turkey and the ­Balkans.

If the Islamic State wants to inflame a religious war, what better place to attack than Rome? A significant strike at a Christian holy site would fit both its self-stated strategy and its building narrative.

Our Italian allies are well aware of this and are responding with the correct initial steps, including placing portions of both their military and the capable Carabinieri paramilitary forces on higher alert, adding more nautical patrols between Libya and their southern islands; sharing intelligence throughout NATO and European Union/Interpol channels; and publicizing these measures to appear a more hardened target.

What else can done?

First, NATO must get into the game. Italy should convene a discussion under Article IV of the NATO treaty, which permits any member to bring security matters before the North Atlantic Council in Brussels. Such discussions are typically used for issues considered particularly concerning, and they occasionally lead to common action under Article V (the famous “an attack on one shall be regarded as an attack on all” clause).

 When Turkey felt threatened by Syrian air activity several years ago, NATO responded by sending Patriot batteries to defend Turkish airspace. Those batteries remain today. In the case of Italian concerns about Islamic State infiltration, Standing NATO Maritime Groups could likewise be used to support the overloaded Italian Coast Guard and Navy.

Second, ramp up intelligence collection. The Italians need access to the highest levels of intelligence being collected in Libya. This means working not only through U.S. and NATO channels but also approaching the Arab nations in the anti-Islamic State coalition for assistance. There is no substitute for on-the-ground assets.

Third, focus even more on the maritime threat. This means using the Italian fleet and Coast Guard to patrol and map the patterns of movement across the central Mediterranean; using long-range patrol aircraft from Sicilian bases; cooperating fully with neighboring Malta, which sits astride the sea lane; and employing high-endurance drones to maintain real-time awareness of maritime activities.

Fourth, and most important, develop a strategy for addressing the problem at its source: in Libya. Given the increasing anarchy in Libya, it is tempting to simply write it off. But eventually, Libya will succeed — it has big oil reserves, an educated population and enviable geography, as it is close to Europe and has a huge seacoast.

Europe needs a strategy to help move Libya toward stability. This means exploring a U.N. or European Union peacekeeping mission; supporting the relatively moderate, internationally recognized government centered in Tobruk; and cooperating closely with Egyptian efforts to take on the Islamic State militarily with targeting, intelligence, financial support and, potentially, airstrikes. In the United States, we can support Italy by helping to lead a Western effort to stabilize Libya.

Just as Churchill saw Italy as a relatively easy gateway to Europe, the Islamic State has geographic, political and symbolic interests in sailing to Italy. We must do all we can to help Italy prepare.

By James Stavridis led the 2011 intervention in Libya as the 16th supreme allied commander at NATO. Now a retired U.S. Navy admiral, he is the dean of the Fletcher School of Law and Diplomacy at Tufts University.