Germany and the US have confirmed that they are sending tanks to Ukraine in a show of support for the government in Kyiv.
The German government said it will be sending 14 Leopard 2 tanks to Ukraine, while the US is planning to deliver 31 Abrams in the coming months.
Germany has also given the go-ahead to a number of other European countries which want to send their own German-made Leopard 2 tanks to Ukraine.
The UK, which has already committed 14 of its own tanks, has welcomed the announcements.
More than 30 countries have provided military equipment to Ukraine since Russia's invasion in February 2022.
Ukraine's President Volodomyr Zelensky has said his forces need Western battle tanks urgently to defend its territory and to push Russian troops out of occupied areas.
Some Western officials believe that Russian forces are currently in a weak position and that these more advanced tanks could help Ukraine to push Russian troops back.
The Leopard 2, used by a number of European countries, is easier to maintain and requires less fuel than some western alternatives.
In the months which followed the Russian invasion, Western nations were keen to offer Ukraine Warsaw Pact rather than Nato standard weaponry, because Ukraine's armed forces had a ready supply of trained crew, spare parts and maintenance capabilities.
Switching to Nato standard tanks would have required a range of logistical support which Ukraine did not have in place.
Kyiv believes its forces are now in a position to use more Nato standard equipment.
The UK has agreed to provide 14 Challenger 2 tanks to Ukraine. The Challenger 2 is the British army's main battle tank.
The Challenger 2 was built in the 1990s, but is significantly more advanced than other tanks available to Ukraine's armed forces.
Ukraine used Warsaw Pact designed T-72 tanks prior to the invasion, and since February 2022 has received more than 200 T-72s from Poland, the Czech Republic and a small number of other countries.
Announcing the US decision to send 31 Abrams tanks to Ukraine, President Joe Biden described them as "the most capable tanks in the world".
He said the US would start training Ukrainian soldiers to use them immediately but it remains unclear how long it will be until the tanks themselves are delivered.
The BBC's Gary O'Donoghue in Washington says the funding process for the tanks means they may not be deployed for several months.
Military professionals point out that success on the battlefield requires a vast range of equipment, deployed in coordination, with the necessary logistical support in place.
The Stryker is one of the many armoured vehicles that have been donated to Ukraine. The US recently confirmed that 90 Strykers would soon be dispatched.
Among the other vehicles donated by the US recently were 59 more Bradley infantry fighting vehicles. They were used extensively by US forces in Iraq.
In December, the US also announced it was sending the Patriot missile system to Ukraine – and Germany and the Netherlands have recently followed suit.
This highly sophisticated system has a range of up to 62 miles (100km), depending on the type of missile used, and requires specialised training for Ukrainian soldiers, likely to be carried out at a US Army base in Germany.
But the system is expensive to operate – one Patriot missile costs around $3m.
Since the start of the conflict, Ukraine has been using Soviet-era S-300 surface-to-air systems against Russian attacks.
Before the conflict began in February, Ukraine had about 250 S-300s and there have been efforts to replenish these with similar systems stockpiled in other former Soviet countries, with some coming from Slovakia.
The US has also provided Nasams (National Advanced Surface-to-Air Missile System) to Ukraine. The first Nasams arrived in Ukraine in November.
In addition, the UK has provided several air defence systems, including Starstreak, designed to bring down low-flying aircraft at short range.
Germany has also provided air defence systems, including the IRIS-T air defence systems which can hit approaching missiles at an altitude of up to 20km.
Among the long-range rocket launchers sent to Ukraine by the US are the M142 High Mobility Artillery Rocket System or Himars. Several European countries have also sent similar systems.
Himars are believed to have been central to Ukraine's success in pushing Russian forces back in the south, particularly in Kherson in November.
Crucially, the range of Himars, and many other systems, varies according to the munitions used, and it is believed that western donors have not provided the ammunition with the longest range.
The munitions thought to have been supplied to Ukraine give the system a range of about 50 miles (80km), which is further than the Smerch system on the Russian side.
Himars systems are also much more accurate than the equivalent Russian systems.
In the months following the invasion and Russia's retreat from Kyiv, much of the war centred on the east of the country where supplies of artillery to Ukraine were in heavy demand.
Australia, Canada and the US were among the countries to send advanced M777 howitzers and ammunition to Ukraine.
The range of the M777 is similar to Russia's Giatsint-B howitzer, and much longer than Russia's D-30 towed gun.
Thousands of Nlaw weapons, designed to destroy tanks with a single shot, have also been supplied to Ukraine.
The weapons are thought to have been particularly important in stopping the advance of Russian forces on Kyiv in the hours and days following the invasion.
Drones have featured heavily in the conflict so far, with many used for surveillance, targeting and heavy lift operations.
Turkey has sold Bayraktar TB2 armed drones to Ukraine in recent months, whilst the Turkish manufacturer of the system has donated drones to crowd-funding operations in support of Ukraine.
Analysts say the Bayraktar TB2s have been extremely effective, flying at about 25,000 feet (7,600m) before descending to attack Russian targets with laser-guided bombs.
Additional reporting by Tom Spencer. Graphics by Gerry Fletcher and Sana Dionysiou.
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