Since Ukraine gained independence in 1991, security co-operation with the UK has been key.
With aspirations to join both the EU and NATO, initial military assistance to Ukraine was focused around defence reform, planning and building.
In 2014, in response to Russia's annexation of Crimea and the crisis in Eastern Ukraine, allies significantly stepped up their support – at the request of the Ukrainian Government.
A year later, the UK launched Operation Orbital, a non-lethal training and capacity-building operation for the Ukrainian armed forces.
In contrast to the US, the UK ruled out providing lethal arms to Ukraine at the time – with Germany and France also opposing the arming of Ukraine at the time.
In 2020, the MOD announced the UK will lead a multinational maritime training initiative to boost Ukraine's Navy.
Watch: Defence Secretary confirms 'light anti-armour defensive weapons' for Ukraine amid Russia tensions.
And the UK and Ukraine launched the Naval Capabilities Enhancement Programme to develop Ukraine's naval capabilities.
This included Ukraine purchasing two Royal Navy Sandown-class minehunters, help in building new naval bases in the Black Sea and Azov Sea and the development and joint production of eight missile warships.
To date, more than 21,000 Ukrainian military personnel have trained under the initiatives.
Earlier this month, the Defence Secretary confirmed the UK would provide "self-defence" weapons to Ukraine amid tensions with Russia.
It marks the first time the UK has supplied lethal weaponry to Ukraine, although it has provided £2.2m of non-lethal military equipment.
British personnel will also provide initial training on how to use the systems under Operation Orbital.
However, it is not just the UK that has provided Ukraine with military assistance.
Since 2014, the US has provided Ukraine with more than $2.5bn in security assistance – including military training and equipment.
Watch: Which UK anti-tank missile is Ukraine getting as Russia tension rises?
The Obama administration provided significant non-lethal military equipment to Ukraine, supplemented over the course of 2015 with a package of military assistance worth $75m.
This included Humvees, surveillance drones, night vision devices and military ambulances.
It wasn't until the Trump presidency, however, that the US started providing Ukraine with lethal weaponry.
This saw the US provide Ukraine with Javelin anti-tank missiles, as well as sniper rifles, rocket-propelled grenade launchers and two retired US coast guard patrol boats.
In March 2021, the US Department of Defense announced a further $125m military assistance package to Ukraine.
This was followed up with further packages in June and September 2021, with the US now considering further assistance due to Russian activity on Ukraine's borders.
NATO also has an assistance package in place with Ukraine, promoting defence reform through capacity building and development programmes.
In June 2020 Ukraine was granted Enhanced Opportunity Partner status, giving the country preferential access to NATO exercises, training and exchanges of information.