With the world waiting on tenterhooks, watching closely to see if or when Russian troops may invade Ukrainian territory, a familiar story is playing out.
Just as Catherine the Great did hundreds of years before him, Vladimir Putin is looking to secure an important strategic area, tamp down influence from rival powers and re-establish Russia’s power on the world stage.
Like Catherine, Putin faces resistance from the Ukrainians holding fast to their independence, and from neighbouring leaders prepared to counter Russian dominance.
But the shape of the political landscape and the nature of modern warfare have changed the game significantly.
Today’s Ukrainians will have far more intelligence about any incoming threat than their ancestors were working with, thanks in large part to the information gathered by their allies.
Last week, US President Joe Biden told his Ukrainian counterpart Volodymyr Zelenskyy there was a distinct possibility Russia could launch an invasion in February.
But Russia maintains that the military build-up around its borders is not a threat, and Ukraine has called on its Western allies to avoid stirring “panic” by talking up the threat of war.
So how will we know if Russia has stepped up from strengthening its defences to a full-scale invasion?
Experts are split on whether Russia will actually invade
All eyes are on negotiations about NATO’s expansion into eastern Europe, which Russia strongly opposes.
Mr Putin’s government has been strengthening its defences along the Ukrainian border since early March.
World leaders have become increasingly nervous over the last few weeks after Russia deployed all five Eastern Military District (EMD) commands into Belarus under the guise of “joint exercises”.
It means the troops “are essentially deploying as close to ready to go as you can be”, according to Janes, a global agency for open-source defence intelligence.
Mark F Cancian, senior international security adviser for the Center for Strategic and International Studies, says there are other “clear signs” Russia is preparing for a military offensive.
This week Reuters reported that supplies of blood were being sent to troops at the border, according to US defence officials.
“There’s no need to store blood if you’re just going to do an exercise,” Mr Cancian told the ABC.
“Plus, they’ve been moving a number of anti-air defence systems, although that can be part of an exercise also.”
There have also been cyber attacks targeting key Ukrainian government websites in recent weeks, which Ukraine blames on Russia.
Similar attacks in the past have erased entire networks and caused billions of dollars in damage.
Olga Oleinikova, director of the Ukraine Democracy Initiative at the University of Technology Sydney, says Russia could still create havoc this way without having to send troops into Ukraine.
“How the war may look is more in the hybrid sphere. So it will be in cyber attack scenarios, damages to infrastructure, and so on,” Dr Oleinikova said.
“Many people are leaving Ukraine, investors are pulling their money out of Ukraine at the moment.
“So this whole panic and this Western discourse of imminent Russian invasion actually does a lot of damage to Ukraine.”
She doubts there will be a full scale conflict in Ukraine. Sara Meger, a Ukraine expert and international relations lecturer at the University of Melbourne, agrees.
But if Putin were to decide to attack, Russia has some options at its disposal.
Recent history gives us some clues about the first signs of invasion
The last time Russia waded into Ukrainian territory by force was in February 2014, with the annexation of Crimea.
Russia seized its opportunity following Euromaidan, a turbulent period of protests prompted by Ukrainian president Viktor Yanukovych’s refusal to sign a free trade agreement with the EU in favour of closer ties with Russia.
After the president fled, Russia sent in special forces.
They took control of a ferry terminal on the Kerch Strait, where Russia borders the Crimean Peninsula, and sent ships to the Black Sea Fleet port at Sevastopol in the south.
Masked troops without insignia poured into Simferopol and took control of key government and strategic sites, raising Russian flags over the buildings and erecting barricades outside.
More soldiers, dubbed “little green men” for the unmarked uniforms they wore, established security checkpoints along the strip connecting the peninsula with mainland Ukraine, and blocked access to airports.
Within hours, Crimea had effectively been cut off from Ukraine.
Russia also focused on communications, cutting off Ukrainian TV channels across Crimea, and replacing some with Russian stations.
Days later, a pro-Russian leader installed in Simferopol called a referendum on Crimea breaking away from Ukraine, and Russia formally annexed the region.
Ukraine has still not accepted Mr Putin’s declaration that Crimea is rightfully part of Russia, and a key bone of contention driving the current conflict is the status of Luhansk and Donetsk in the eastern Donbas region.
Fighting between Ukrainian troops and separatist rebels backed by Russian forces in the region continues to this day.
So what would an escalation look like?
Mr Cancian says if Russia does decide to invade, there are two options as to how this could play out.
The “little option” would see a limited operation in the Donbas area where “maybe they bite off another piece of Ukraine”.
“The big option is the one you see on many maps, with forces converging on Kyiv, or a notion of creating a land bridge between Crimea and the Donbas,” he added.
“Those will be much, much larger operations … a much broader set of military capabilities than just biting off a piece.”
But he says that kind of large-scale invasion seems unlikely.
“The small option is much more feasible. They can bring a lot of combat power to bear in a small area and be relatively confident of success,” he said.
“The big option is much riskier. Personally, I don’t think the Russians have the forces to do one of these big operations — a land bridge, or the attack on Kyiv.
“Those 120,000 Russian troops sound like a lot, but keep in mind that when the Soviets and the Germans faced off over this area in World War II, the Russians had well over a million men.
“So 120,000 is not that big when you consider the vast territory that’s involved.”
Mr Cancian says the first signs of Russian escalation would be a movement of troops along the borders, drone overflights or reconnaissance, or even artillery bombardment.
But Ms Meger is sceptical of Russia pursuing a ground offensive, suggesting if there was an escalation from the West — if it opted to station troops inside Ukraine for example — Vladimir Putin may pursue an “aerial offensive”.
“[Russia] would then claim that as a defensive or pre-emptive attack, perhaps,” she said.
But invasion will not mean immediate victory for Russia. Some experts suggest Putin will be unlikely to take the whole country and, more importantly, hold it for any significant period.
The Ukrainians would be expected to put up a good fight
Civilian resistance to Russian force has been growing since fighting began in 2014, with ordinary Ukrainians ready to take up arms and defend their independence.
A recent survey found roughly a third of the population would be willing to join an armed resistance if an invasion took place.
In the fallout of the Crimean annexation, private militias sprung up around the country, establishing themselves as the first line of defence against Russian pressure.
Ukraine’s Territorial Defence Force, the volunteer reserves, have recently been running training drills in the woods outside Kyiv, with former military officers showing civilians the basics.
But the Ukrainian military says it won’t stand a chance against the Russians without significant military support from the West.
“There are not sufficient military resources for repelling a full-scale attack by Russia if it begins without the support of Western forces,” the head of Ukraine’s military intelligence service told the New York Times.
Experts are also sceptical of the Ukrainian military’s ability to defend against a Russian attack.
“The Ukrainians will still resist fiercely, and it’d be a lot of fighting, but the Russians could bring all their firepower to bear and have a very good chance of success,” Mr Cancian said.
Ms Meger agrees, suggesting that despite significant expansion over the past eight years of conflict, Ukraine’s military still lacks the heft of Russia’s.
“The US, Western European countries and Canada have provided a lot of military assistance and training. But when I was there doing field work, speaking with members of the armed forces in 2017, they were just woefully under-equipped, under-trained and under-resourced,” she said.
“That’s why they can’t even defend against a couple of separatist groups. If Russia actually wanted to invade, they would sweep through, just like they did with Crimea.”
The US has 8,500 troops on stand-by in the event that Russian forces do enter Ukraine, and British Prime Minister Boris Johnson is also considering sending troops to NATO countries in the Baltic region as a show of strength.
Are we close to an invasion?
That’s the million-dollar question that no-one but Mr Putin himself can answer right now.
Mr Cancian says if Russia is going to escalate, February is the danger zone.
“I don’t know that this week is more dangerous than last week. But the Russians are in a position where they could do something quite quickly,” he said.
“When you get into March, it gets to be the mud season, which doesn’t make combat impossible, but just really slows things down.
Ms Meger doubts there will be an invasion.
“I don’t think Russia will act … I think they would only take military action defensively,” she said.
“So, if they actually saw US troops or any sort of Western allied troops in Ukraine on that eastern border.
“But I don’t think either side would be so foolish as to let it escalate to that point.”
Instead, Ms Meger suggests the next step, perhaps from both sides, is “a lot more rhetoric”.
“But the danger of rhetoric is it could actually force the hand of some party to have to follow through,” she said.