After weeks of merely containing Ukraine's incursion in the Kursk region, Russia has begun fighting back.
Ukraine had early success when its troops smashed their way into western Russia last month, seizing hundreds of square kilometres across the region.
The surprise attack was an embarrassment for Russian President Vladimir Putin, and Moscow was criticised for its "slow" and "scattered" response.
But that may all be about to change.
Moscow has launched its counteroffensive, already reclaiming several settlements, according to a senior Russian commander.
Analysts say if this is the start of a major pushback, and Moscow really "flexes its muscles", then Kyiv could be in trouble.
Russia will 'outnumber them and outgun them'
On August 6, Ukraine burst through the border into Kursk with thousands of troops.
They were supported by swarms of drones and heavy weaponry, including Western-made arms.
It was the largest foreign attack on Russia since World War II.
Ukrainian troops advanced rapidly, and set up a military administration in the Russian territory they seized.
The plan was to hold onto the 1,300 square kilometres of land Ukraine claims to control "indefinitely", President Volodymyr Zelenskyy said.
If they could, it would give Mr Zelenskyy bargaining chips to potentially bring an end to the war.
[map]But over the last two days, Russia said it had reclaimed 10 settlements in the area around Snagost, on the western flank of the area occupied by Ukraine.
Chechen special forces commander Major General Apti Alaudinov announced Russian troops had gone on the offensive.
"The situation is good for us," he told Russia's TASS news agency.
"A total of about 10 settlements in the Kursk region have been liberated."
He claimed that Ukrainian troops were suffering heavy losses and "are starting to realise that holding the territory won't be a cakewalk".
Mr Zelenskyy confirmed Russia had begun "counteroffensive actions".
He said it was "going in line with our Ukrainian plan".
Geolocated footage indicated that Russian forces retook positions east of Zhuravli, and had advanced north and north-east of Snagost, according to analysis by the US Institute for the Study of War (ISW).
The ISW said at this stage the size, scale, and potential prospects of the Russian counterattacks were unclear.
Sydney University's professor emeritus Graeme Gill, an expert in Russian politics, said Ukraine's incursion was never going to be sustainable.
And if Russia attacks with "gusto", Ukraine would struggle to match their manpower, drones and artillery.
"They will outnumber them and outgun them," Professor Gill said.
"Ultimately, when Russia flexes its muscles there, Ukraine is not going to be able to maintain the incursion."
Incursion failed to halt eastern advances
Ukraine's top commander, General Oleksandr Syrskii, said one of the key objectives of the Kursk attack was to divert Russian forces from other areas, particularly eastern Ukraine.
But fighting in the Donbas region — Ukraine's industrial regions of Donetsk and Luhansk — instead gathered pace.
And Russian forces were now only a few kilometres outside the strategic industrial hub Pokrovsk.
The International Committee of the Red Cross (ICRC) said three of its staff were killed on Thursday after shelling hit the site of a planned frontline aid distribution in the Donetsk region.
The agency said it operates regularly in the area and its vehicles are clearly marked.
[map]Anatol Lieven, director of the Eurasia program at the Quincy Institute for Responsible Statecraft, said despite the Kursk incursion, the balance of advantage remained with Russia.
"A key objective of the operation was to divert Russian troops from eastern Ukraine where they are on the offensive and that hasn't seemed to have happened," he told the ABC's Late Night Live.
He added there were reports Ukraine might have diverted many of its "elite troops" away from the eastern frontline to Kursk.
"That would be quite a serious error from a Ukrainian point of view," he said.
Russia said it had advanced by 1,000 square kilometre in eastern Ukraine in August and September.
Open-source data and battlefield reports indicate it was the fastest they had advanced in Donbas in about two years.
'It was a mistake'
Professor Gill said Ukraine had made the situation in the east worse for themselves by staging the Kursk incursion.
"I think it was a mistake," he said.
"If the Kursk incursion was about trying to draw troops away from Donbas and relieve the situation there, it doesn't seem to be successful."
But there have been other reasons given for the attack.
Mr Zelenskyy said the Kursk operation was an attempt to force Mr Putin negotiate an end to the conflict, and to carve out a buffer zone to prevent attacks on the neighbouring Sumy region.
He has also been using it as leverage to push for more support from the West.
Particularly to get the US to change its stance on allowing Ukraine to use its long-range missiles to strike deep inside Russian territory.
Professor Gill said Ukraine was showing the West it was capable of continuing to fight, telling them "if you give us the weapons, just think what we could do".
"If the incursion was meant to actually be a play for greater support from the West, well, then you might say it's successful," he said.
But he believes it will be difficult for Kyiv to remain in Kursk if Russia ends up mounting a large counteroffensive.
"If they are pushed out, it may in a sense undercut all those aims," he said.
"In a sense, it's a trap of their own construction."
US President Joe Biden and British Prime Minister Keir Starmer are meeting in the United States on Friday amid signs both Washington and London are growing more receptive to allowing the Ukrainians to use their arms to hit targets farther inside Russia.
Their meeting comes after US Secretary of State Antony Blinken wrapped up a three-nation, Ukraine-focused tour of Europe, where held extensive discussions with officials about how the war was developing.
"What we learned from our Ukrainian partners will inform discussions that we'll be having with other allies and other partners in the days and weeks ahead, as we work through and think through the coming months," Mr Blinken said.
