Five things to know about Ukraine's Kursk incursion

Russia said on Saturday it had fully regained control of its Kursk region on the border with Ukraine, after an unprecedented Ukrainian incursion aimed at bringing the war onto Russian territory and influencing eventual negotiations.

Ukraine's army denied Russia's claim to have driven Kyiv's forces out of Kursk, saying "statements by the enemy leadership about the 'defeat' of the Ukrainian troops are nothing more than propaganda tricks".

Here are five things to know about the incursion, which took Russia by surprise when it was launched in August 2024, a key development in the now over three-year war sparked by Russia's February 2022 invasion of its neighbour.

- Unprecedented action

With the incursion, Ukraine brought war into Russian territory for the first time since World War II.

This gamble allowed it to temporarily regain the initiative at a time when Russian had been slowly gaining ground in eastern Ukraine for months.

In just a few days, the Ukrainian army managed to capture 92 towns covering more than 1,200 square kilometres, an area slightly larger than the size of Hong Kong.

By Friday evening, only a few square kilometres remained in Ukrainian hands, with the Russian army advancing toward the border village of Gornal, according to the US-based Institute for the Study of War (ISW).

- Bargaining chip

Ukrainian President Volodymyr Zelensky's stated objectives were to "destroy as much Russian war potential as possible" and "create a buffer zone" against Russian bombing in northern Ukraine.

"If we talk about potential negotiations, we will have to bring the Russians to the other side of the table. On our terms," added a senior advisor to Zelensky, Mykhailo Podolyak.

But once the Russian territories were seized, keeping them proved difficult for Kyiv. It could not afford to redeploy troops fighting against Russian forces in the east of Ukraine.

The strategy of using the territory gained as a bargaining chip in eventual negotiations also lost some significance after Donald Trump became US president. He opened direct negotiations with Moscow while pressuring Kyiv to end the conflict.

- North Korean involvement

Announcing to President Vladimir Putin that all the Kursk region, including Gornal, had been "liberated", Russia's Chief of Staff Valery Gerasimov for the first time acknowledged the involvement of North Korean soldiers in the Russian counter-offensive.

According to South Korean and Western intelligence agencies, more than 10,000 soldiers from North Korea were sent to Russia last year to help Moscow's fight against the incursion.

Gerasimov hailed the "heroism" of the North Korean soldiers, who he said "provided significant assistance".

Zelensky has said more than 12,000 North Korean soldiers were involved, with more than 3,000 of them killed or wounded.

- Counter-offensive

With the North Korean help, the Russian army was able to launch a counteroffensive. By February, nearly two-thirds of the territory conquered by Ukraine in Russia had been recaptured.

"The Kyiv regime's adventure has completely failed," Putin told Gerasimov. Russian troops are now at the border and are poised to beef up threats to the Ukrainian region of Sumy, which faces Kursk. Moscow has already carried out incursions there in recent weeks.

Ukrainian forces continue to occupy some pockets of Russian territory along the border in the northwest of the Belgorod region, according to ISW.

- Symbolic region

The Kursk region has immense historical resonance in Russia and throughout the former Soviet Union.

It was outside the city of Kursk in the summer of 1943 at the height of World War II that Nazi German and Soviet forces waged one of the biggest battles in the history of warfare, resulting in a decisive victory for the USSR.

The battle, a key turning point in World War II, is known as the biggest tank battle of all time, involving some 6,000 tanks on both sides.