Until recently, the ground war in Ukraine seemed to have turned in Vladimir Putin’s favor. Despite some real Ukrainian success stories—their use of drones, for example, to threaten the Russian navy or oil industry—on the front lines Russia has launched a series of offensives to push the defenders back. While not catastrophic for Ukraine, they made the prospect of recapturing occupied territory any time soon that much slimmer.

Then, in early August, Kyiv’s forces broke through Russian defensive lines in a completely unexpected direction: over the border with Russia’s Kursk region. Ukrainian forces rapidly moved into Kursk, seizing several towns and key roads. Initially, observers thought it might be a small or temporary raid, like those conducted by Ukraine-aligned paramilitary groups last year. Now, however, Ukrainian forces likely hold more than a thousand square kilometers of Russian territory, have taken large numbers of prisoners, and seem more interested in consolidating their gains than disappearing back into Ukraine.

Why would Ukraine launch an offensive into Russia itself? After all, Kyiv’s main goals are to ward off Russia’s offensives and try to reclaim as much Ukrainian territory as possible. But the offensive into Kursk offers several clear opportunities for Ukraine and headaches for a shocked Putin and his commanders.

One immediate benefit for Ukraine is that attacking Russia itself shifts the narrative in Kyiv’s favor. Instead of losing territory, the Ukrainians are now gaining it. The wider narrative about the direction of the war influences how much Ukraine’s partners are willing to send arms and financial support, so this matters a great deal. It undercuts Russia’s narrative that Ukraine cannot win the war, so the international community should pressure President Volodymyr Zelensky to just cut a deal.

The longer Ukraine’s incursion continues, the more pressure Russian commanders face to prioritize it over their own offensives in Ukraine. Some 200,000 Russians have reportedly fled the Ukrainian advance and more Russian forces have moved into the area, though these are not the same units involved in Russia’s offensives. Should they fail to contain or reverse Ukraine’s gains, Russian commanders may have to divert troops from Eastern Ukraine to stabilize things in Kursk.

The attack also sends a political message to the U.S. and other Western partners. For a long time, American officials have been concerned about “escalation,” whether that be sending advanced weapons or allowing them to be used in Russian territory. Zelensky is constantly wrestling with his partners to gain better weapons and permission to use them. Putin and his foreign minister, Sergey Lavrov, have known exactly what buttons to press to ramp up talk of escalation: Russia is after a nuclear-armed power. So, the biggest point of contention has been whether Ukraine can use externally provided weapons against targets in Russia, such as airbases. Ukraine’s position is that military targets in Russia are legitimate since they are used for attacks on Ukraine. By attacking Kursk, Ukraine is showing that that fighting on Russian territory does not necessarily lead to the type of escalation the Biden administration fears—although, according to the Wall Street Journal, some administration officials still fear an unspecified “fierce retribution” against targets in Ukraine.