Ukraine’s invasion into the Kursk region of Russia shocked Ukrainians, their allies, and most of all, Russia.

Ukrainian units have mounted brief, overnight raids into Russian territory before, including one into the Kursk region — near Russia’s western border — earlier this year. But those were quick incursions followed by hasty retreats. This time is different: Ukraine has managed to capture nearly 400 square miles so far, as well as hundreds of Russian soldiers.

The Ukrainian offensive began more than a week ago, on August 6. Ukrainian troops — how many is unclear, though US officials have said several thousand — and armored vehicles crossed the border from northeastern Ukraine. It’s also unclear how much fighting has taken place, though reporting suggests Ukrainian forces have faced at least some Russian defenses.

Ukraine has yet to say what its military objective is, and it likely has more than just one. No officials other than President Volodymyr Zelenskyy have spoken publicly about those objectives; the president said that “Russia has brought war to others, and now it is coming home.” Still, the sustained invasion has proved to be a morale boost for Ukrainians sorely in need of one after two and a half years of grinding war.

Russia’s response to the Kursk operation has been extremely slow. Part of that may be because its military apparatus is extremely hierarchical — which can delay rapid action as decisions work their way up the chain — and because it has gone through major destabilizing changes of late. Crucially, its forces are also tied up in Ukraine’s east, where they have been making gains in recent months.

Russia’s rhetorical response has also been quite muted. President Vladimir Putin and the Kremlin’s military apparatus are referring to efforts to rebut the Ukrainian advance as an anti-terror campaign rather than a full military operation. Part of Russia’s strategy overall has been to simultaneously portray its war in Ukraine as existential and not that serious; it refers to its invasion as “a special military operation,” making it sound less concerning to Russians than an all-out war, and assures them that it doesn’t affect their lives.

Ukraine’s strategy in the Kursk region makes that harder to maintain, since so far around 200,000 Russians have evacuated from their homes due to the invasion — and the Russian government is only offering about $115 to compensate.

Ukraine’s continuing incursion into Russia is politically useful, especially in drawing attention and potentially support from US and other allies. Two and a half years into the war, global attention has shifted away from Ukraine’s front line to Israel’s war in Gaza, and now the upcoming US elections.

Support for Ukraine has waned within the US, too. Republicans in Congress have tried to cut or eliminate critical US military assistance, and overall US support could be at risk if Republican presidential candidate Donald Trump manages to recapture the White House in November.

This successful and sustained incursion into Russia indicates that Ukraine is still a very disciplined fighting force that can actually successfully execute on battlefield objectives with sophisticated strategy. Reminding outside powers that Ukraine can be militarily successful, and could still win this, could help shore up support that’s crucial for maintaining the flow of ammunition, fighting vehicles, fighter jets and spare parts, and other gear.

The invasion is also beneficial practically. To counter Ukraine’s attack, Russia will need to pull some troops from the front line in Ukraine. However, its options are limited for doing so; it is trying to avoid redeploying soldiers away from fighting in Ukraine’s Donetsk region, which Russia falsely claims is its own territory.

Troop movement is already occurring according to Riley Bailey, a Russia analyst at the Institute for the Study of War, though not at the scale that Russia really needs to repel the attack and regain territory.

“We’ve seen reports of up to 11 Russian battalions redeploying from other sectors of the front to form kind of this hastily-put-together force grouping in Kursk Oblast,” Bailey told Vox. That part of the border was poorly defended on the Russian side, which probably influenced Ukraine’s decision-making.

It’s impossible to predict what impact Ukraine’s offensive will have on the end of the war. But it will have an immediate, wider-ranging effect, particularly for Russia, Bailey said. “They’re going to have to make a whole lot of theater-wide decisions that they otherwise weren’t going to make before.”

And ultimately, the incursion could also give Ukraine leverage further down the road, in the form of prisoner swaps and potentially negotiations to end the war — if, that is, they’re able to hold on to the territory.

Ukraine has been extremely tight-lipped about the entire operation thus far, which speaks to a high level of operational sophistication. But there’s a serious question as to how long Ukraine can maintain this operational tempo and whether they can hang on to this territory — which they plan to do, according to Katarzyna Zysk, professor of international relations and contemporary history at the Norwegian Institute for Defence Studies.

Ukraine has already committed troops to this incursion who could also be effective on other front lines; in trying to force Russian resources from the east, it’s diverting its own from a crucial front.

Ukraine is already struggling with troop numbers, and there’s simply a limit to the number of people it can mobilize.

Back in July, according to a Reuters report, morale was flagging; Zelenskyy had lowered the draft age from 27 to 25, and fighters on the front have become exhausted after two years of nonstop battle.

And even if this battlefield success turns into a successful recruitment drive, that doesn’t mean that suddenly Ukraine will have thousands of highly qualified and effective soldiers.

“Inasmuch as you can get anyone to drive a truck or clean toilets, you can’t get effective warfighters that easily,” Mathieu Boulègue, a defense analyst for the Center for European Policy Analysis, told Reuters.

Ukraine remains outnumbered and outgunned; Russia is obtaining drones, ballistic missiles, and ammunition from partners like Iran, China, and North Korea, and is still working on improving its weapons manufacturing domestically, though that’s somewhat challenging given the sanctions on its economy.

And the Kursk invasion doesn’t change the fact that Russia is still devastating Kharkiv and has made advances in Crimea, although part of the Kursk invasion seems to be aimed at weakening Russia’s air capabilities and potentially further mobilize forces away from Crimea.

As of now, Ukraine’s sneak attack may have disrupted the idea that Russia — and Putin — is in control of the war. But it hasn’t yet significantly eased pressure on the eastern front line or stopped Russia’s assaults on Ukrainian cities and towns. It will be increasingly difficult for Ukraine to sustain this level of intensity as more Russian reinforcements arrive — and that’s exactly what needs to happen for Ukraine to be able to have real leverage over Russia in future territorial exchanges or peace negotiations.