On 6 August Ukrainian infantry and armoured units crossed the frontier into the Kursk Oblast and began the first substantial offensive into Russia by a foreign power since the Second World War.

Ukrainian Armed Forces (UAF) seized operational surprise, a rare occurrence in a war characterised for the past year by grinding position warfare where movement has been difficult and very costly.

In 10 days Ukrainian forces have advanced more than 20 miles and control nearly 450 square miles of Russian territory. More than 80 settlements have fallen into Ukrainian hands and Russia has been forced to evacuate as many as 150,000 civilians.

What is being called Ukraine’s Kursk incursion is a stunning turn of events in a conflict that has been until now fought entirely on Ukrainian soil.

But this undeniable success is a high risk operation. Why have Ukraine’s leadership taken this gamble? What are the aims of this operation? How could it affect the course of the war?

The Ukrainian incursion likely has three chief objectives.

The first is operational: to draw Russian armed strength northward in order to relieve pressure on the Kharkiv and Donbas regions to the east and south, where fighting has been very heavy and the UAF have been hard pressed to hold ground.

So far this effort has achieved limited success. Russia has reportedly begun moving units northward from Zaporizhzhia and Dnipro in the south toward the Kursk region. But Russia’s military leadership has resisted withdrawing heavy weaponry and armoured battalions from Donetsk and Kharkiv where the fighting is most fierce.

Although president Vladimir Putin and Russian’s leaders describe the effort to halt the Ukrainian advance as a counter-terrorist operation, the Kremlin is clearly unsettled. Most defence commentators agree that it will be necessary to deploy significant military power to dislodge Ukrainian forces.

The days and weeks to come will provide interesting insights into the capacity of the Russian army to learn from the mistakes it made early in this war and mount a swift and effective counterattack.

The second key aim is to send a political message to its own population, to Russia's people and its leaders and to the rest of the World, that Ukraine remains capable of seizing the initiative. The operation has also succeeded in attracting the attention of the western news cycle back to the war in Ukraine after it had been fixed almost exclusively on the Middle East.

For months coverage of the Ukraine War has been dominated by talk of relentless Russian advances against a Ukrainian army with its back to the war, suffering heavy losses and running low on heavy weapons, ammunition and especially manpower.

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The UAF’s surprise advance was prepared in secret. It was preceded by impressive electronic warfare that successfully jammed Russian digital and electronic surveillance systems while at the same time denying access to Ukrainian communications. This operation demonstrates rumours of the UAF’s imminent demise were massively exaggerated.

The third major Ukrainian aim is to alter the war’s fundamental strategic logic. It has achieved this aim in two ways.

Up until now virtually all of the heavy fighting has taken place in Ukraine and not on Russian soil. This state of affairs was dictated by restrictions on Ukraine imposed by western powers who have supplied them with heavy and advanced weaponry on condition it was not to be used inside Russia.

This restriction, combined with the relatively narrow theatre of operations in the east and south, allowed the Russians to leave more than a thousand miles of their border with Ukraine very lightly defended.

By ignoring western wishes, the UAF has demonstrated that Russia is vulnerable to attack across this long frontier. This should force the Russian army to deploy more of its resources to defend the whole border with Ukraine with the happy consequence of weakening its effort to the east and south.

(Image: EVGENIY MALOLETKA)

Driving home this reality could have a beneficial longer-term effect on possible peace negotiations by showing that Russia too is vulnerable to an attack from its neighbours. Ukraine has not been criticised by any western power for taking this decision.

But the risks that come with this operation are substantial. The further Ukrainian forces extend into Russian territory, the more vital lines of supply are extended and the greater the danger that a powerful Russian counterattack might roll up the flanks of the UAF, surrounding some of its best units which might be forced to choose between surrender or annihilation.

Wider geo-political uncertainties, in particular the outcome of the US presidential election, no doubt convinced president Volodymyr Zelensky and the Ukrainian leadership that they had no choice but to accept these risks in an effort to seize the initiative from Russia.

Professor Peter Jackson is chair in global security at the University of Glasgow and director of the Scottish Council on Global Affairs