But there are growing signs that Europe’s biggest land war since 1945 is entering a much more deadly phase as battle nears major cities.

Russian forces appear to be regrouping amid an attempt to get a stranglehold on the country’s capitol of Kyiv. Experts increasingly believe Putin’s military, once regarded as among the world’s most powerful, in fact lacks the troop strength and combat effectiveness to seize and control Kyiv, one of Europe’s largest cities, let alone the entire country against the strong resistance Ukraine is mounting.

That leaves Russia’s strongman with fraught options: Retreat, suffer heavy losses in urban fighting, or resort to total destruction.

“I’m highly skeptical of them actually being able to secure Kyiv,” Jeffrey Edmonds, an expert on the Russian military with the Arlington, Va.-based research organization CNA, told Insider.

“They can level it, which is what their preferred technique is. It remains to be seen if they try to actually control the city street by street or if they just level it in the hopes that the Ukrainians give up.”

If Russia continues its invasion, Putin faces the prospect of a deadly quagmire similar to the invasion of Afghanistan that contributed to the collapse of the Soviet Union. Or he risks inflicting mass casualties on the Ukrainians with whom he’s pledged fraternity, calling them and Russians “one people.”

Russia’s currency is cratering amid a global backlash, as its top officials show few signs of backing off. They insist the invasion of Ukraine on three sides is a “special military operation” and have banned Russian media from calling it a war. In this bind, the specter of European cities bombed beyond comprehension, clouds of chemical weapons or the blast of a tactical nuke, are no longer unthinkable, albeit unlikely.

After its months-long military build-up of over 160,000 troops, Russia’s initial offensive was perplexing. Troops moved in small groups rather than in combat formations which could have effectively seized territory and defended themselves. Russian air support was non-existent, and little artillery was coordinated to aid their advance. Troops outran their own logistics support. Russia used main roads to advance and created its own miles-long traffic jam.

This invasion force seemed focused on a lightning strike to take the country’s largest cities and kill or capture its elected leader, President Volodymyr Zelenskyy. From embattled Kyiv, Zelenskyy has rallied his nation and much of the world to his cause.

“I don’t think they can control the entire country, what I think they’re trying to do is control certain key objectives like Kyiv and Kharkiv, Mariupol,” Edmonds said in a Wednesday phone interview. “That seems to be the overarching plan here is to seize the center of gravity, which is Kyiv. Replace the political structure and have the rest of the resistance fall apart.”

But Russian stumbles and a resolute Ukrainian force parried that lightning strike.

“The Russian failure is driven by the fact that they’re attempting to conduct a full-scale invasion without the mil operation that it would require, thinking they can avoid most of the fighting,” Michael Kofman, an Russian military expert also at CNA, said on Twitter after the first four days of war.

In another tweet he said that “It seems they tried to win quickly and cheaply via ‘thunder runs.'”

That effort, which he called “shambolic,” has continued as Russia’s numerically superior force tries to encircle the capital.

One drone video shows a gaggle of Russian tanks on an avenue on Kyiv’s outskirts that get attacked. Rob Lee, a former Marine and senior fellow at the Foreign Policy Research Institute, said on Twitter that Russian troops displayed “very poor tactics” by inadvertently bunching so many tanks within range of Ukrainian indirect fire like tanks and artillery.

That’s the big challenge for the Russians, coming into the city. Ben Wallace

That’s the big challenge for the Russians, coming into the city. Ben Wallace

The ensuing battle of Kyiv is likely to reveal the Russian military’s true colors.

Russian soldiers who enter the capital will face an entrenched and well armed enemy without the air power they need. Tanks will be crippled, crews captured. Infantry and fighting vehicles will need to coordinate their movements in a way that have not done yet in this war if they hope to defeat ambushes, evade snipers and thwart petrol bombs from multiple directions in a dense cityscape like Kyiv.

When asked about Russia’s chances here, Edmonds, the military expert, recalled his days as a US Army tanker at the outset of the Iraq war.

“Think about Iraq, we hardly used tanks at all. I drove around the city in a Humvee without doors in 2003, and then we went into up-armored things. The idea being, you flood the city. Tanks didn’t have much of a role there.”

Fighting well in a city requires not only coordination, command and control, and air power, but also a lot of practice via the kind of urban war games that Russia hasn’t routinely done.

Edmonds said they mostly train to fight NATO, and in open spaces. And even a highly trained force still runs the risk of heavy casualties, a point made by another Western veteran closely following the conflict.

“That’s the big challenge for the Russians, coming into the city,” Ben Wallace, the UK defense secretary who is a British Army veteran, said in an iterview  with “BBC Breakfast” that aired on March 2.

“That’s where everyone from civilians throwing Molotov cocktails to soldiers with anti-tank weapons can inflict very serious damage onto armed forces.

“I was a former soldier — we always accepted [that] the casualty rates in cities and urban areas was very, very high.”

Which brings us to Option B.

‘Putin is not going to reverse anything’

Experts use a one-word shorthand to describe it: Grozny.

In 1999, Putin was the head of the FSB security agency, plucked from relative obscurity to lead Russia. He launched an offensive to recapture the breakaway region of Chechnya, whose fierce fighters had fought Russian forces to a standstill a few years before.

Russia heavily outnumbered the Chechen fighters but largely chose to fire on the Chechen capital of Grozny rather than enter it and face these defenders. Russia pummeled the city with missiles, thermobaric weapons, bombs and artillery. One cruise missile struck a central market and killed 140, according to an account by Geoffrey York, a Globe and Mail correspondent who reported from Grozny.

After four months, Russian forces captured the smoldering city and ended the siege. An estimated 25,000 civilians were killed. Years later, the UN called Grozny the most destroyed city on Earth.

He has no sustainable political endgame in the face of what is going to be fierce resistance from Ukrainians William Burns

He has no sustainable political endgame in the face of what is going to be fierce resistance from Ukrainians William Burns

CIA Director William Burns said Putin had planned to seize Kyiv within two days. But his forces were unable even to encircle it in two weeks, causing Burns to describe Russia as “largely ineffective” against the ferocity and heroism of Ukraine’s defenders.

“I think Putin is angry and frustrated right now,” Burns told the House Select Intelligence Committee on Tuesday. “He’s likely to double down and try to grind down the Ukrainian military with no regard for civilian casualties.”

But the biggest challenge, Burns continued, is that “he has no sustainable political endgame in the face of what is going to be fierce resistance from Ukrainians.”

There are even claims that Russia may resort to chemical weapons, as a pressing debate grows about whether Putin could eventually turn to a tactical nuclear weapon to force Ukrainians to submit. (When Insider brought up this possibility with Edmonds, he replied: “Non-zero chance, man.”)

But Putin, experts and officials alike worry, has put his chips all-in.

“Putin is not going to reverse anything,” Edmonds said. “He’s going to keep throwing what he can at this in an attempt to get his political objectives, which I don’t think he can get.

“That’s why this thing ends poorly.”