President Vladimir Putin’s career of pursuing revenge and redemption for Russia converges on this moment, as the United States presents him with a path off the ledge that he’s stepped onto along the border with Ukraine.

The dangerous standoff over Ukraine appears to continue after Tuesday’s virtual summit between Putin and President Biden. The initial White House readout was terse and opaque. The statement said Biden had expressed “deep concerns” about Russia’s actions, and warned that the United States and its allies “would respond with strong economic and other measures in the event of military escalation.”

Biden also “called for de-escalation and a return to diplomacy.” U.S. officials have said that means a new attempt to implement the 2014 and 2015 Minsk protocols, signed after Russia seized Crimea and sponsored a proxy war in eastern Ukraine. This diplomacy will require “follow up” discussions, the White House said.

Will Putin take this path over the next few weeks and months? Or will he continue to threaten invasion if he doesn’t achieve his demand for a formal pledge that Ukraine will never join NATO — something Biden has ruled out? Putin’s wisest strategy would be to take a Minsk exit ramp and claim it as a victory. But stubborn, self-infatuated leaders sometimes do stupid things.

Let’s imagine that despite Tuesday’s phone diplomacy, Putin is reckless enough to press into Ukraine with the 175,000 troops U.S. intelligence says he is ready to bring into the battle. What would happen then?

Putin in the first days would face a messy war in Ukraine itself. Ukraine’s military isn’t a match for Russia’s, but it’s a lot more potent than the military he faced when he seized Crimea in 2014. Ukraine has better training, equipment, electronic-warfare skills and battlefield experience than before.

Putin, strangely, has abandoned the stealthy approach that worked for him in 2014. By massing nearly 100,000 troops on the border, he disdained the gray-zone tactics of hybrid war — the “green men” that swiftly seized key targets in Crimea. He can’t play this hybrid game now because U.S. intelligence has outed his secret plans for a full-scale war.

Ukraine also has an aggressive military intelligence service, commanded by Brig. Gen. Kyrylo Budanov. He planned a bold sting operation last year to capture Russian mercenaries who had fought inside Ukraine. Though it failed, it was a taste of what Ukrainian covert operators could do in a real conflict.

Beyond the battle against uniformed troops and intelligence operatives, Putin would probably face a prolonged guerrilla war from Ukrainian militias. Knowledgeable sources estimate that more than 400,000 pro-Kyiv Ukrainians have received at least some training since Russia’s 2014 incursion, and that there are at least 1 million weapons in private hands, including AK-47s and other automatic weapons looted from government stores. As many as 15 militia groups are spread throughout the country — some virulently right-wing, but all capable of causing havoc for Moscow (and probably Kyiv, too).

“Beyond the response from the U.S. and allies, the Ukrainians will fight fiercely,” says William B. Taylor, a former U.S. ambassador to Kyiv. He predicts “guerrilla war for sure if the Russians invade and try to stay.”

Putin would face immediate battlefield risks, but the longer-term consequences could be far worse, even if he installed a government subservient to Moscow. If Biden followed through on his threats, Russia’s economy would be wrecked. Never strong under Putin, it would become feeble as a united Europe and the United States imposed sanctions that sources tell me might include cutting Russia off from the SWIFT system of international payments — literally turning it into a pariah state.

A Russia that went to war in Ukraine would have only China as a reliable ally. That might console Putin, but it should panic Chinese President Xi Jinping. The China-Russia axis would cement a “decoupled” world in which the United States and the technologically advanced democracies would have a huge, and probably lasting, advantage over Moscow and Beijing.

And, finally, there is the X-factor: the danger that a war in Ukraine would blow back into Russia and Belarus. Polls conducted by the Levada Center in Moscow show that Putin’s campaign to suppress Ukraine doesn’t appear to have majority support in Russia. As the casualties mounted, so would the political pressure on Putin and his authoritarian friends.

Going into Tuesday’s virtual summit, many commentators saw Putin in the driver’s seat against a weakened United States. Biden has his problems, but Putin would be very foolish if he imagined that a Ukraine war would be a cakewalk.