Western leaders have long misunderstood Vladimir Putin.
In 2001, President George W. Bush "looked the man in the eye" and "found him to be very straightforward and trustworthy." Not exactly.
In 2015, President Barack Obama predicted that Mr. Putin would not want to "get bogged down in an inconclusive and paralyzing civil conflict" in Syria. Five hundred thousand slaughtered Arabs later, Mr. Putin has propped up his client, dictator Bashar al-Assad.
Angela Merkel made Germany dependent on Russian energy in the belief that Mr. Putin's ambitions would drown in a river of euros. The chancellor was mistaken.
And after Mr. Putin dismembered Georgia in 2008 and annexed the Crimean Peninsula in 2014 (while inserting irregular forces into eastern Ukraine to wage an endless insurgency) American and European leaders went out of their way not to provoke him.
Which may explain why President Biden, early in 2022, hoped Mr. Putin was planning only a "minor incursion" into Ukraine.
A question worth asking: Should Mr. Putin come out of this war looking and feeling like a winner – I'm hopeful about the current Ukrainian counteroffensive but I rule nothing out – what would he do next? The answer, I assure you, will not be: "I'm going to Disneyland!"
Moldova is the lowest hanging fruit. It's not a NATO member and its military capabilities are limited. Russia already occupies Transnistria, a strip of what used to be eastern Moldova between the Dniester River and the Ukrainian border. Moldova would probably fall to Mr. Putin within days.
Mr. Putin might want to formalize his control of Belarus, to which he recently deployed tactical nuclear weapons.
After that, perhaps a bolder move: the creation of a land bridge to Kaliningrad, a Russian territory – it was Königsberg when it was captured from Germany in 1945 – 400 miles west of the Russian mainland.
Headquartered in Kaliningrad is the Russian Navy's Baltic Fleet. Russian troops there are equipped with mobile nuclear-capable Iskander-M missiles, and sophisticated air defense systems.
Russian tanks would roll west into Lithuania from Belarus and east into Lithuania from Kaliningrad. Mr. Putin would need to take only a ribbon of southern Lithuania, in particular the main road running from Belarus to Kaliningrad.
But Lithuania is a NATO member, so Mr. Putin wouldn't dare, right? Don't be so sure. He'd likely call the invasion "a special military operation to restore Russian territorial contiguity at a time of increased NATO aggression against Russia."
He might also charge that the Russian minority in Lithuania, roughly 7 percent of its 2.8 million population, is being oppressed and requires his help. Neighboring Latvia and Estonia, where ethnic Russians are close to a quarter of the population, could be dealt with later.
Mr. Putin could say to NATO: "I'm open to diplomacy – a land for peace deal. But if you'd rather wage war, you should understand that extreme measures will be considered."
Now ask yourself: Which NATO members would be willing to risk a nuclear war with Russia over a ribbon of countryside in the southern Baltics? Turkey? Germany? France? Would most Americans support such a conflict?
But it's tough to see how NATO could survive if it failed to defend one of its members as pledged in Article 5 of the North Atlantic Treaty.
For Mr. Putin, NATO's collapse would be a huge victory, one that his Communist allies in Beijing and his Islamist allies in Tehran would regard as a significant battle won in their war against the West.
And in both those capitals, as well as in nuclear-armed Pyongyang, a lesson would be learned: The U.S. and Europe cave to nuclear blackmail.
There's one additional geostrategic reality I want to mention. Sandwiched between Lithuania on the north and Poland on the south is the Suwalki Gap, a narrow stretch of Polish land running from Belarus to Kaliningrad.
A rail link just north of this corridor links Kaliningrad to the Russian mainland. But it functions under an agreement between Russia and Lithuania whose relations are now severely strained.
A year ago, Lithuania, complying with European sanctions, prohibited the transit of coal, metals, and building materials. Kaliningrad's governor called that a "serious violation" of the agreement.
A Russian invasion and occupation of the Suwalki Gap also would trigger Article 5. And it would cut off Lithuania, Latvia, and Estonia from their NATO allies, complicating any attempt to provide materiel and reinforcements in case of a Russian invasion.
Not just coincidently, comrade, two years ago, Russian and Belarusian troops staged a military exercise to practice closing off the Suwalki Gap and attacking Lithuania.
Perhaps you'll say that, after the war in Ukraine, Mr. Putin wouldn't have the resources and manpower necessary for such aggressions. But, if he's been successful, Tehran and Beijing would be as helpful as possible. The morale of his troops would improve. And he'd have millions of Ukrainians whom he could draft and then – with bayonets pressed against their backs – use as cannon fodder.
This much we should understand by now: Mr. Putin's mission, as he sees it, is to restore the Russian Empire which, for less than a century, was re-branded as the Union of Soviet Socialist Republics.
"If Russia is not defeated [in Ukraine], then it will just be a matter of time before it regroups, re-arms, and that it will come for somebody next," Lithuanian Prime Minister Ingrida Simonyte told a reporter last month.
In the Pentagon and at NATO headquarters in Brussels, geopolitical strategists should be imagining scenarios such as those described above. Defense plans based on deterrence rather than appeasement should be finalized. A good place to do that would be the next NATO summit. It's scheduled for July in Vilnius, the Lithuanian capital.