BBC
Fighting has raged in Ukraine since Russia launched a full-scale invasion in February 2022. Russian forces have slowly expanded the amount of territory they control over the last year, mostly in the east of Ukraine, but Ukrainian forces have made those advances as slow and difficult as possible and even staged a counter-offensive into Russian territory.
Here is a recap of recent significant events and the situation in Ukraine.
Expanded capabilities
In November, Ukraine reported its troops had engaged in combat with North Korean troops in the Kursk region of Russia.
Moscow and Pyongyang have not responded to the claim that North Korean soldiers have been under fire, but US intelligence and Nato have confirmed there is evidence of North Korean troops being involved in Russia's war.
The arrival of North Korean troops was cited by US officials as a reason for President Biden giving the green light for Ukraine to use long-range ATACMS missiles to strike inside Russia.
How that decision will affect the war in the coming months is still to be seen, but Ukraine now has the potential to hit targets almost 200 miles (300km) from the Russia-Ukraine border.
Ukraine sends units into Russia
The appearance of North Korean troops in the Kursk region was a response to a surprise attack launched across the border by Ukrainian troops in August, advancing up to 18 miles (30km) into the Russian region.
Almost 200,000 people were evacuated from areas along the border by the Russian government and President Vladimir Putin condemned the Ukrainian offensive as a "major provocation".
After two weeks, Ukraine's top commander claimed to control more than 1,200 sq km of Russian territory and 93 villages. The regions of Kursk and Belgorod have both declared a state of emergency.
Some of that territory has been regained by Russia but Ukraine still has troops in the Kursk region.
The counter-offensive is seen partly as an attempt to
force Russia to redeploy units from the east and relieve pressure on the beleaguered Ukrainian defences there, and partly as a bid to improve Ukraine's chances of a peace settlement.
Russian incursion north of Kharkiv
At the beginning of May 2024, Russian forces crossed the international border to the north of Ukraine's second-biggest city, Kharkiv. Several villages were seized and thousands of civilians fled.
Russia's main offensive has long focused on the eastern Donetsk region, but this was one of the most significant ground assaults since the start of the war and further stretched Ukraine's front-line defences.
The Russian push took place at the end of a four-month period when the US was not supplying weapons to Ukraine, due to a stalemate in the US Congress.
The issue was finally resolved at the end of April, when the US passed a $61bn aid package to provide missiles, artillery and air-defence systems to the Ukrainian military.
Ukrainian forces eventually held firm and even though the city of Kharkiv has come under repeated attack from glide bombs fired by Russian warplanes, it remains beyond the range of Russian artillery.
Russia grinds forward in the east
The incursion north of Kharkiv was some distance from the main front line in the east where Russia has continued its offensive operations and been edging forwards since October 2023.
Eastern Ukraine has been contested territory since 2014, when Russian-backed fighters seized large swathes of the eastern Donetsk and Luhansk regions.
Russia's biggest advantage is manpower and it has shown a willingness to
throw soldiers at Ukrainian positions to gain a few metres at a time.
According to the UK chief of defence staff Sir Tony Radakin, more than 1,500 Russian soldiers were being killed or wounded every day in October. That is the highest rate since the beginning of the war, exceeding the 1,200 being killed or wounded every day in May and June.
Experts at the Institute for the Study of War believe Russian forces will likely continue to focus on seizing frontline Ukrainian towns and cities this winter with the city of Pokrovsk as one of their main targets.
The Russian advance towards Pokrovsk is the most notable change in control of the front line near Donetsk for several months, but innovative tactics by Ukrainian forces, combining the use of drones and ground forces, appears to have held up a direct assault by the Russians and inflicted significant losses of troops and equipment.
The recent defence of Pokrovsk follows the Ukrainian withdrawal from Avdiivka, just north of Donetsk, back in February after months of fighting.
Almost all of Avdiivka's pre-war population of more than 30,000 people have left and the town itself is almost completely destroyed.
To the north, areas around Bakhmut have remained a flashpoint and have endured some of the heaviest fighting of the war.
Although Ukraine gained some ground around Chasiv Yar, which is situated on high ground some 10km west of Bakhmut, Russian forces have since made further advances in the area.
Two and a half years of fighting
Russia's invasion began with dozens of missile strikes on cities all over Ukraine before dawn on 24 February 2022.
Russian ground troops moved in quickly and within a few weeks were in control of large areas of Ukraine and had advanced to the suburbs of Kyiv.
Russian forces were bombarding Kharkiv, and they had taken territory in the east and south as far as Kherson, and surrounded the port city of Mariupol.
But they hit very strong Ukrainian resistance almost everywhere and faced serious logistical problems with poorly motivated Russian troops suffering shortages of food, water and ammunition.
Ukrainian forces were also quick to deploy Western supplied arms such as the Nlaw anti-tank system, which proved highly effective against the Russian advance.
By October 2022, the picture had changed dramatically and having failed to take Kyiv, Russia withdrew completely from the north. The following month, Ukrainian forces recaptured the southern city of Kherson.
Since then, the battle has mostly been in the east of Ukraine with Russian forces slowly gaining ground over many months, with
at least 70,000 Russian troops killed - and an estimated 500,000 being either killed or injured in total, according to the UK Ministry of Defence.