The arrival of a fleet of Russian warships at Havana is a reminder that the enemies of freedom are closer than one might like to think — just 90 miles off the coast of Florida. At a time when many Americans would like to shrug off the burdens of global leadership, the port visit from President Putin’s navy underscores that defending liberty in faraway places like Ukraine, Israel, and Taiwan is preferable to facing hostile weaponry at close range.

Mr. Putin’s dispatch of four ships, including the frigate Admiral Gorshkov and the nuclear submarine Kazan, signal “that Moscow can challenge Washington in its own sphere of influence,” American University’s William Leogrande says. The visit is less than two weeks shy of President Biden giving Ukraine permission to use American ordnance to strike targets inside Russia and Mr. Putin’s warning that his military might respond with “asymmetrical steps.”

The saber-rattling by Mr. Putin also signals to “Russia’s friends in the region,” one analyst tells the AP, including America’s “antagonists Cuba and Venezuela, that Moscow is on their side.” A Pentagon spokeswoman, Sabrina Singh, assures that the vessels “pose no direct threat” from the military viewpoint. The symbolic nature of the visit, though, amounts to a provocation that is in itself a kind of danger to America and the free world. 

Feature the very name of one ship that just steamed into Havana, the Admiral Gorshkov. The vessel is the namesake of Admiral Sergei Gorshkov, the head of the Soviet navy between 1956 and 1985. He transformed the Soviet fleet “from a coastal defense force into a formidable global strategic force,” the New York Times has said, and was the “driving force behind the Kremlin’s decision to build a fleet of submarines and surface ships to rival” America’s. 

If Admiral Gorshkov personified “the Soviet Union’s naval might,” as the Times put it, Admiral Gorshkov itself poses a threat beyond any mere symbolism. The frigate and its companion Kazan can fire cruise missiles with a range of 1,000 miles and anti-ship missiles with a 350-mile range, the United States Naval Institute warns. Admiral Gorshkov is also loaded with Russia’s latest advancement in rocketry: Zircon hypersonic missiles. 

Mr. Putin touts Zircon missiles “as a potent weapon capable of penetrating any existing anti-missile defenses,” the AP reports, “by flying nine times faster than the speed of sound.” They have a range of more than 600 miles, enabling Russian ships “to loiter off the coastline of the United States or another NATO member and strike key command and control centers with minimal warning,” the Georgetown Journal of International Affairs reports.

It was to avoid perils like this, in part, that President Monroe uttered his namesake doctrine in 1823. He warned Europe’s powers, including Russia, that it would be “impossible” for America to view their “interposition in any form” in the Americas “with indifference.” When Russian ships darkened a harbor in Venezuela in 2008, these columns wondered if the doctrine “will need dusting off.” Is Mr. Biden willing, or able, to do so today?

President Theodore Roosevelt cited the Monroe Doctrine to stress America’s readiness “to repel any wrong, and in exceptional cases to take action” in the hemisphere. America, he said, was willing to act “in our own interest as well as in the interest of humanity at large.” That spirit underpinned the global expansion of our military responsibilities over the course of the 20th century. Today, a kind of neo-isolationism looks to scale back America’s role.  

It’s reasonable to question the value of, say, aid for Ukraine when the money is needed at home, and America’s debt soars. The arrival of Russian ships at Havana, though, illuminates the logic of defending our allies abroad. That was the argument of an architect of American Cold War policy, Senator Vandenberg. America’s support is necessary because, “though other independent peoples are in nearer jeopardy,” Vandenberg said in the 1940s, “we are the final target.”