Russian forces are massing on Ukraine's border. Here's what Russia watchers think could be Putin's next big move.

• Russia has massed a lot of troops, weapons, and equipment along Ukraine's border.
• Some experts think Putin wants a negotiated solution and will gradually escalate while offering chances for concessions.

Russia has moved tens of thousands of troops, along with weaponry and equipment, into positions near Ukraine. The situation is alarming, and experts are torn on what Russia's next move might be in this developing crisis.

Some observers think Russia is still interested in a negotiated solution, possibly through gradual, coercive escalation, while other experts believe that Russia is done talking and is currently preparing for a full-scale invasion of its neighbor.

In the event that Russia moves to invade, the scale of the Russian buildup to the country's north, east, and south offers assault options to escalate ongoing fighting, seize a portion of the sovereign state's territory, or swallow Ukraine whole, some experts told Insider.

Russia has repeatedly denied having plans for hostile action against Ukraine, but Western leaders are skeptical. President Joe Biden said just last week that his "guess" is that Russian President Vladimir Putin will escalate and take some action against Ukraine, saying the Russian leader "has to do something."

It is difficult to discern exactly what Russia's next move could be though. Gustav Gressel, a senior policy fellow at the European Council on Foreign Relations, told Insider that "there is an endless amount of scenarios we can think through on how Russia might want to escalate."

'It'll sort of turn nasty'

"Putin has a lot of flexibility in how he might deploy forces," Andrew Lohsen, a fellow in the Europe, Russia, and Eurasia Program at the Center for Strategic and International Studies, told Insider.

The Russian president, he explained, "still has options that he can use that would put pressure on Ukraine and the West short of actually sending anything across the border."

Lohsen said that he expects "him to escalate gradually so he can increase the pressure and give Ukraine and give the West the chance to make concessions before he moves further."

He said that Russia might opt for harmful yet limited action, such as cyberattacks against critical Ukrainian infrastructure. Putin could also deploy some troops and push along existing battle lines in eastern Ukraine, intensifying an eight-year conflict that has claimed more than 13,000 lives.

Russia could "show the pain the Russian forces can cause" and then give Ukraine and the West "a chance to react and to come to the table," he said.

If Russia decides to further escalate the current crisis, turning it into a more serious conflict, Lohsen explained that Russia's current force posture permits potential attacks along at least three fronts, creating a very challenging situation for Ukraine's defenders.

Ukraine could find itself facing a concerted Russian offensive involving not just the pro-Russian separatists it has battled for years but also Russian troops backed by air power, artillery, and other long-range strike options.

"What I assume will not happen is a full-scale invasion overnight, just a jump from a threatening posture to full war," Gressel said. "My guess is that it would be a step-by-step approach to such an escalation."

"It'll sort of turn nasty," he said. "It can turn nasty very quickly, but it would be a gradual development." And if and when the situation takes a turn for the worse, Ukraine is likely to face a daunting situation.

Ukraine has a long border that it shares with Russia and Belarus, and it can be difficult to predict where the attacks will come from, so when an attack comes, the Ukrainians will have to quickly move troops and equipment to combat those attacks.

"That is an invitation for the air force to crush them," he said, explaining that the Russian air force, "after one, two, maybe three days, will be done reducing Ukraine's air force to nothing and will then be free to engage ground targets almost at will."

Gressel said that Russia could try to execute a strategic bombing campaign while supporting a puppet government in the Ukrainian capital but argued that such actions were unlikely to yield the desired submission.

"Moscow, sooner or later, will arrive at the point where it realizes that unless you drive to Kyiv by tank and sort government affairs out by yourself, you will not get the result you want because Ukrainians generally do not want to sacrifice independence and sovereignty," he said.

Gressel predicted "there will be resistance even if Russia wins the conventional fight." He suggested that the Russian military may face an insurgency for which it might not be prepared given Russia's often misguided perceptions of the Ukrainians.

Ukraine fields a military of an estimated 250,000 personnel, a force large enough to offer pockets of strong resistance to Russian invaders. In the event of a Russian takeover, elements of these forces could combine with armed citizens and militia to mount a bloody insurgency. Current and former Ukrainian officials have threatened just this strategy.

"We are going to fight if something happens," a Ukrainian official recently told CNN. "Our people are ready to fight. Every window will shoot if [Russians] go [in]."

'They're going big on this'

Jeffrey Edmonds, a former military analyst with the CIA and current Russia expert at CNA, told Insider that a coercive course of action involving gradual escalation seems less likely than jumping directly from the current aggressive posture to a major military offensive given the escalatory actions Russia has already taken.

"I don't think they're going for an extended campaign of coercion," he explained. "I think they're actually waiting until they have what they want to have on the border before they invade. At this point, I think the decision has been made."

Experts said that if Russia attacked Ukraine, it would likely need a pretext, some justification, real or falsified, to sell the conflict back home and internationally.

The Biden administration recently revealed that US intelligence indicated that Russia has operatives in place in Ukraine, potentially to conduct false-flag operations in advance of any Russian military action.

The opening phase of the armed conflict likely to follow, Edmonds said, would probably involve what the Russians consider non-contact warfare: ranged strikes from land, sea, and air to cripple the opposing force, giving Russia air superiority and greater freedom of movement.

Next, Ukraine could be looking at a very significant ground force offensive from the north, east, and south. CSIS recently created a map that reflected what that invasion might look like and published it in a report by Seth Jones, director of the International Security Program at the think tank.

Edmonds suggested Russia might also pursue an amphibious landing around Odessa. Jones also suggested this possibility in his analysis

Though not completely necessary, such a landing could be valuable were Russia to decide to seize the entirety of Ukraine rather than stopping at the Dnepr River and attempting to force some settlement from there. Such a maneuver could also be a kind of feint to draw away defenders from the main offensive.

Half a dozen Russian landing ships previously operating in the Baltic Sea were spotted recently heading to the Mediterranean, from which they could relocate to the Black Sea if Russia needed these ships to do so, The Drive reported over the weekend.

Another possibility, suggested by CSIS's Jones, would be a southern sweep that seizes all of Ukraine's coastline, possibly even connecting Russia with Transdniestria, a breakaway territory wedged between Moldova and Ukraine.

Russia's seizure of Crimea gave it a port on the Black Sea, from which Russia could land more troops in Ukraine as part of this southern strategy, troops that could then link up with forces coming from the east.

Edmonds added that his guess is "that the offensive is going to go west of Kyiv," possibly putting the Russian military close to NATO. "I think they're going big on this," he said.

"And I think it's going to happen in the next couple of weeks," he said, adding that there likely will not be any strategic indicators it is coming. "It's just going to happen, and it's going to happen pretty fast."

'More open confrontation between Russia and NATO'

The Biden administration revealed in early December that intelligence pointed to a possible "early 2022" invasion with a force of as many as 175,000 Russian troops. Russia does not have that many troops in place, but it is continuing its buildup.

Commenting on the Russian buildup near its next-door neighbor, Secretary of State Antony Blinken said last week that "we know that there are plans in place to increase that force even more on very short notice."

He added that this gives Russian President Vladimir Putin "the capacity, also on very short notice, to take further aggressive action against Ukraine," explaining that this situation has not only the US' attention, but also that of allies and partners in Europe.

The White House said last week that a military offensive against Ukraine could come "at any point."

In addition to vocalized support for Ukraine's territorial integrity, the US has provided military aid to Ukraine along with NATO allies and warned that Russia will face severe economic and financial consequences if it invades. Biden told reporters last week that Putin has "never seen sanctions like the ones I promised to impose if he moves" on Ukraine.

Russia has given no indication that it intends to de-escalate, and NATO has been strengthening its positions in eastern Europe, sending more warships and fighter jets into the area. On Monday, the Pentagon said that 8,500 US troops are on high alert for a possible deployment to Europe in support of NATO.

Experts say there is a real risk that Russian military action in Ukraine could exacerbate tensions between Russia and NATO and potentially ignite a larger conflict, especially if Russia feels its security is threatened.

"If we see some sort of open conflict in Ukraine, then we'll for sure enter an era of more open confrontation between Russia and NATO," Lohsen said.

"Russia has now overturned some of the core beliefs and frameworks of European security," he said, explaining that "we are entering into a time when conflicts are probably going to appear more often or could be more deadly because we no longer have agreed rules of what is acceptable behavior."

"I think this brings us back to an era of expansionist conflicts and basically rewinds the clock."