Kyiv's battle tank line-up is about to look very different after the US and Germany this week finally gave approval to send highly sought-after heavy Western weapons to Ukraine.
Berlin bowed to intense international pressure and announced it would send 14 of its Leopard 2 A6 tanks to the battlefield and also approved shipments by allied European states.
Washington then pledged to send 31 American-made M1 Abrams to Ukraine, ending months of refusal.
Both offers come soon after Britain committed 14 Challenger 2 tanks to the war effort.
Tanks provide a level of direct firepower, mobility and protection for the Ukrainian land forces that no other system, such as artillery, infantry, helicopters or drones, can.
The new array of powerful weapons is expected to breathe new momentum into Ukraine's fight and help it claw back ground that has fallen to Russia.
Kyiv has called it an "important game changer", with the foreign minister enthusiastically tweeting that "the tank coalition is formed".
So what makes these particular tanks so superior?
And what are some of the possible drawbacks?
Leopard 2 — The best in the West
Developed in the 1970s by German defence company Krauss-Maffei Wegmann, the Leopard 2 tank is regarded as one of the West's best.
The manufacturer goes as far as claiming it's "the world's leading battle tank".
It is equipped with sophisticated technology and was specifically engineered for the European theatre, Ian Langford, a retired military officer and national security expert, told the ABC.
"It's essentially capable of destroying all Soviet or Russian armour," he said.
Germany has built more than 3,500 Leopard 2s since beginning production in 1978.
It is one of the most widely used Western tanks.
This not only means that several nations may be able to tap into their supplies to send tanks to Ukraine, but it will be easier for Kyiv to manage maintenance and crew training.
"Perhaps most critically, the Leopard is integrated into the NATO system of ammunition, equipment and materials so you can sustain, maintain and replace them very quickly," Mr Langford said.
The Leopard weighs more than 60 tonnes, has a 120mm smoothbore gun and a fully digital fire-control system.
It is a four-crew tank with a range of about 500 kilometres, and top speeds of about 70 kilometres per hour
It uses technology such as optics and laser rangefinders that allow it to sense and anticipate the older-made Soviet armour that Russia relies on.
"It can look beyond the visible horizon and can therefore manoeuvre to advantage in that context," Mr Langford said.
Unlike the US Abrams tanks, Leopards run on diesel fuel rather than jet fuel.
"So if need be, you can literally pull up at a service station and fill them up, as opposed to the really high-performance fuels that other tanks like Abrams have to rely on," Mr Langford said.
There have been reports that heavy tanks like the Leopard will have mobility issues, especially when trying to cross rickety Soviet-era bridges.
But Mr Langford said they were known to operate easily over Eastern European roads, rail and infrastructure.
Any limiting factors were not specific to tanks, and other conflicts had shown that they were better at navigating tricky terrain than other equipment, he added.
"Because it's got tracks and the ground pressure that means you can distribute the weight so that it can run over some of those bridges," Mr Langford said.
"The question around whether the Leopard is appropriate and even capable of operating in Eastern Europe is a bit moot because they're actually designed for that."
America's M1 Abrams
Until now, the US had resisted providing its own M1 Abrams tanks to Ukraine, citing extensive and complex maintenance and logistical challenges with the high-tech vehicles.
Just last week, Colin Kahl, the Pentagon's top policy adviser, told reporters the Abrams were complicated, expensive, difficult to maintain and hard to train people to use.
Carrying a crew of four, Abrams were first deployed to war in 1991.
The tank has thick armour, a 120mm main gun, armour-piercing capabilities and advanced targeting systems.
Variants of the M1 tanks can weigh up to 70 tonnes and they have a maximum speed of about 68kph.
The US has more than 4,000 in stock.
The Abrams tanks use a turbine jet engine to propel themselves. However, they burn through at least seven litres of fuel per kilometre regardless of whether they are moving or idling, which means a network of fuel trucks is needed to keep the line moving.
Where there are benefits to the Abrams is in the protection space, Mr Langford said.
"The Abrams have plenty of armour and armour packs that bring more levels of protection," he said.
However, against Russia's T-72 and T-62 tanks, the Leopard was still superior in protection, he added.
Leo Purdy, a military fellow at the Australian Defence Force Academy, said the Abrams could technically outmatch the Soviet-era T-62, T-64 and T-72 currently on the battlefield.
And they were at least on par with Russia's third-generation T-80 and T-90s on a tactical level, he said.
"In simple terms, these tanks will provide improved firepower, protection and mobility to the Ukrainian armoured forces over the Soviet-era 'T series' tanks," Mr Purdy told the ABC.
"At the tactical level, Western tanks will provide a qualitative advantage.
"And at the strategic level, additional tanks will help counter the numerical advantage of the Russians."
Logistics is a primary issue associated with the Abrams, which may take months to deliver.
Ukraine's military will also have to go through significant preparation to learn to operate, maintain and sustain them.
"Tank technology is important, however how they use them — for example, the doctrine to guide how they fight, and how they are supported — is equally, if not more so [important]," Mr Purdy said.
"If the tank crews are poorly trained and they do not employ their tanks using a combined-arms fighting approach with adequate logistics support, then tanks become vulnerable."
The timing for both the delivery of the tanks to Ukraine and the training of Ukrainian troops is unclear.
"While I expect Ukraine will no doubt appreciate these tanks, having three different kinds of Western tank (and potentially multiple versions of the Leopard 2), in addition to the various Soviet-era 'T' series tanks will cause some logistic headaches as it will require three different sets of training for both the crews and the maintenance teams," Mr Purdy told the ABC.
US officials have only said it will take "many months" to deliver the Abrams tanks, but the Leopards will arrive faster.
A handful of Challenger 2s
Britain announced earlier this month it will send 14 of its Challenger 2 tanks to Ukraine.
The Challenger 2 was introduced into service in the 1990s and is the British Army's main battle tank.
The army claims that it has "never experienced a loss at the hands of the enemy".
The Challenger is a four-crew tank weighing 62.5 tonnes, with a 120mm rifled gun.
Mr Langford said given the small amount the UK was providing, it appeared to be more of a gesture than a move that would significantly boost battlefield capabilities.
"But it's a really important one as the British try and push partners to continue to donate equipment and materials to Ukraine," he said.
US President Joe Biden said that in total European allies had agreed to send enough tanks to equip two Ukrainian tank battalions, or a total of 62 tanks.
"With spring approaching, Ukrainian forces are working to defend the territory they hold and preparing for additional counter offences," he said when announcing the Abrams approval.
"To liberate their land, they need to be able to counter Russia's evolving tactics and strategy on the battlefield in the very near term."
Kyiv is calling for hundreds of battle tanks from the West.
Mr Langford said it wanted 300 Leopard 2s alone.
Which tanks are currently on the battlefield?
Both Ukraine and Russia have so far been fighting with very similar versions of the same tanks.
These include the T-62, T-64, T-72, T-80 and T-90 main battle tanks.
Many in the T series are left over from the collapse of the Soviet Union and the end of the Cold War.
"In technological terms, both sides have similar tank capabilities," Mr Purdy said.
"However, in numerical terms, the Russians have lots more tanks than Ukraine."
Mr Langford said the T series tanks were difficult to sustain and maintain given that most of their spare parts and equipment came from Russia.
"Because of all the export controls now on the Russian economy, their (Ukraine's) ability to replace and sustain its armour is really limited," he said.
"Their vulnerability is their ability to replace and sustain their tank variants across their fleet."
He added that a lot of the technology was "pretty immature".
"They don't have the sights, the kind of weapons systems and sophisticated sensing suites that the Leopard has," he said.
Even the T-90, which Mr Langford said Russia designed to specifically destroy Abrams, was so far not performing well in Ukraine.
"It hasn't been the game changer that the Russian defence industry had talked about for some time," he said.
"It's just not performing."
With enough modern Western tanks, Ukraine could essentially replace its T series.
Ukrainian President Volodymyr Zelenskyy said the key now was speed and volume.
"Speed in training our forces, speed in supplying tanks to Ukraine, the numbers in tank support," he said.
"We must form such a tank force, such a freedom force, that after it strikes, tyranny will never again rise up."
Story By : Annika Burgess/ABC Wires
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