With the Ukrainian summer approaching fast, the clock is ticking on Kyiv's long-awaited "spring offensive" against Russian occupying forces.
The Russians are prepared for it.
Western governments have supplied much of the weapons and training Ukraine requested ahead of their promised spring attack.
But with fewer than three weeks of spring remaining, President Volodymyr Zelenskyy said on Thursday that, while Ukraine's forces were mentally ready, they still needed time to prepare.
So is this "spring offensive" still coming? What is it? And if it succeeds, what comes next?
The answers may come down to allied support, the element of surprise and, perhaps most importantly, mud.
What's happening now?
Mr Zelenskyy said in an interview broadcast on Thursday by the BBC that they needed to wait for the right time.
"With [what we have], we can go forward and be successful," Mr Zelenskyy said in the interview.
"But we'd lose a lot of people. I think that's unacceptable."
Russia's army, plagued by low troop morale and dwindling weapon supplies, has failed to gain any significant ground in months.
Ukraine's most recent successful push forward was in late summer last year, when they gained significant territory in the country's north-east and later in the south.
Ukraine was able to stall Russia's last major offensive in Bakhmut, but the current stalemate has resulted in one of the bloodiest battles since Russia invaded Ukraine more than a year ago.
By concentrating its own forces in Bakhmut, Ukraine has tied up a large proportion of the Russian military and inflicted heavy losses.
Meanwhile, fighting has continued along the eastern and southern fronts, where neither side has managed to make any real breakthrough.
Now the pressure is on for Kyiv to make sure this attritional conflict will not turn into another stalemate by reclaiming territory from Russian control, and prove it can put advanced Western military assistance to effective use.
In the meantime, Moscow is reinforcing its front lines, digging trenches and trying to make sure their positions are defensible.
Why spring?
Spring was touted as the time when the Ukrainians would likely have donated Western vehicles and weapons in place and their troops trained.
It was expected that by then, Russian forces would be depleted enough to give Kyiv a chance to punch through their fortifications.
But as weather expert and retired US military meteorologist David Helms explained, weather also plays a crucial role.
Mr Helms said weather affected everything from vehicle mobility to satellite surveillance capabilities and the effectiveness of electro-optic equipment.
"The goal there is to see the other guys before they can see you, so you can launch and hit them before they even know you're there," Mr Helms told the ABC.
Last month, Canberra-based defence company Electro Optic Systems signed a $120 million deal to export its Remote Weapons System to Ukraine.
The weapons system is fitted on top of armoured vehicles and tanks to allow troops to identify targets and fire on them without leaving the vehicle.
Other Western countries have also provided night vision equipment which can give a significant advantage in low-vision conditions such as cloudy weather or nights with low moonlight.
Knowledge of weather conditions can allow troops to employ these tools, and at the right time, to get the greatest advantage.
Mr Helm is part of a network of expert digital volunteers monitoring and sharing information that could give Ukraine the upper hand.
"In the military, all this science, all this intelligence — signals intelligence, human intelligence, environmental intelligence — that's the weather guys — they're all being brought to bear," he said.
"I'm hopeful that the Ukrainians will be able to exploit all this intelligence community data and information in formulating their plan."
But one thing that could play an even bigger role in Ukraine's counteroffensive plans is mud.
What is mud season?
Mr Helms described Ukraine's mud season as "a time where roads don't exist".
As the ground thaws out from the winter freeze, the ground usually turns to mud in early spring, making unsealed roads impassable.
The soil will begin to dry across Ukraine from the south, meaning that within a certain window, if timed correctly, Ukraine could advance while Russian tanks are still stuck in the mud.
Predicting when the mud will dry up requires a lot of intricate calculations using data from various weather surveillance technologies.
This year, April experienced unusually high rainfall, extending mud season by about a month.
Such conditions make ground operations, resupply and air support much more difficult to sustain.
Mr Helms said lighter vehicles or tracked heavier vehicles fare better in this condition.
Critical to a "mud counteroffensive strategy" is an analysis of the vehicles and weaponry available to each side.
The element of surprise
Russia and Ukraine's weapon capabilities have both been widely publicised.
Mr Helms said Ukraine was unlikely to come across any surprises among Russia's arsenal when they launched their next offensive.
When it comes to weapons supplied by Ukraine's allies, big-ticket items like the US-made Patriot guided missile systems have been all over the news but there is also a lot that remains classified.
"I wouldn't underestimate the Ukrainians," Mr Helms said, adding that they may have some capabilities yet to be revealed.
Olga Oliker, Crisis Group's program director for Europe and Central Asia, said announcing the arrival of advanced weaponry has a "PR effect" for Ukraine, as does announcing their upcoming offensive.
"They've been getting this influx of Western aid and support, so I think they want to prove that they can do something useful with that," she said.
An element of surprise could still come from the exact timing and location.
"In the days of satellite monitoring of fortifications, troop build-up and movements, the element of surprise is harder to obtain," she told the ABC.
"I think in the best-case scenario, the Ukrainians [will be] able to do something in several places at once."
Dr Jessica Genauer, senior lecturer in international relations at Flinders University, said in an analysis this week that there would likely be a two-stage counteroffensive in the coming weeks.
"[And] a possible second and more decisive attack towards the end of the northern summer, when weather and weapons supplies are maximised," she wrote.
"Overall, it's clear that by September or October this year, Ukraine will need to have shown success in a counterattack to ensure continued weapons supplies from Western partners, or the ability to negotiate peace on beneficial terms."
What will be the objective of this offensive?
Ms Oliker said the object of this offensive was not only to liberate more territory but also to prove that they could do it, to keep the support coming.
Victory would also improve morale amongst the Ukrainian population and within the armed forces.
However, this long-awaited spring offensive is not expected to bring an end to the conflict.
Ms Oliker said no-one would expect Ukraine to regain all its territory in the next few months.
But a successful counteroffensive could make "the Russians realise that they're fighting a losing battle", she said.
"Then potentially you can start having a conversation."
If they do succeed, the immediate challenge will be re-establishing control over liberated territories and providing humanitarian supplies, shelter, medical care and public administration.
She said Ukraine has already learned that when you liberate a territory, the land is badly damaged, it's often heavily mined and will likely continue to face ongoing Russian bombardment.
"People who have stayed are deeply traumatised, so the reintegration of liberated territory is also a pretty substantial challenge," Ms Oliker said.
If Ukraine fails, they could get pressured into asking for a deal.
"And the repercussions outside Ukraine will be no less solemn, teaching dictators either that expansionism is rewarded, or that it's a catastrophic mistake," Ms Oliker said.
