As they drove out of the strategic eastern city of Lyman on Monday, Ukrainian soldiers waved, hooted, and raised their fists in triumph, riding M113 armored personnel vehicles provided by Western countries. They passed eight corpses of enemy Russian soldiers who died while fleeing a Ukrainian counteroffensive that has swept through the area and is still ongoing, putting President Vladimir Putin’s claims of annexation to rest.

The bodies were bloated, and some of them still had open mouths, as if in shock. The dead Russians were being unceremoniously placed into black bags as Ukrainian troops drove by.

Leonid, a soldier with Ukraine’s National Guard, sat atop a tank a few yards away, contemplating Russia’s plans to send 300,000 more men to Ukraine. “They’ll need a bigger grave,” Leonid predicted.

Just two days after Ukrainian troops declared victory in Lyman, a city of 22,000 people that the Russians had used as a vital transport hub in Ukraine’s Donetsk region, there was almost no military presence left there — a sign of how quickly Ukrainian forces are advancing, if at all.

Following Moscow’s “partial mobilization” of 300,000 new troops, Kyiv appears to be making a major push to retake as much occupied territory as possible before those reinforcements arrive.

Forcing the Russians to retreat from nearly the entire northeastern Kharkiv region, and now from Lyman, has placed Ukraine’s military in a strong position to attack the Russians occupying the neighboring Luhansk region, the border of which is only about 15 miles away by road from Lyman.

The State Duma, Russia’s lower house of parliament, voted unanimously on Monday to ratify Putin’s claimed annexation of the Ukrainian regions of Donetsk, Luhansk, Kherson, and Zaporizhzhia, though even the Kremlin spokesman admitted he did not know the precise borders of Russia’s new territories because Russia does not fully control them.

In a separate, slower-moving counteroffensive to the south, the Ukrainians reportedly pushed the Russians back some 20 miles along the west bank of the Dnieper River, as part of an effort to retake Kherson, which fell to Russia early in the war.

Ukraine’s victory in Lyman will be remembered for the message it sent to the Kremlin: Putin’s annexation of the partially occupied regions was a farce. Lyman was very much part of the lands that Putin claimed in a ceremony in Moscow on Friday, but his soldiers left in a hurry just one day later, with some dying on the way out.

Agents from Ukraine’s internal security service, the SBU, interviewed her on Monday about what happened during Russian occupation, including how much Russian rubles she charged for products in her small store. Across the street, forces of the self-proclaimed Donetsk People’s Republic, the Kremlin-aligned separatist regime, had established a police station. But, she claims, they abruptly abandoned the base two weeks ago. Someone spray-painted “How could you?” on the building the next day.

Though the Ukrainian military surrounded Lyman over the weekend, most Russian forces had already left, according to locals. However, a few enemy soldiers may still be hiding in the surrounding woods.

After the Ukrainian military left Lyman in a convoy of armored personnel carriers, a few Ukrainian soldiers pleaded with The Washington Post reporters not to enter the city because it was still dangerous.

Meanwhile, soldiers from Ukraine’s 81st Air Assault Brigade were on the lookout for fleeing Russians on the northern approach to Lyman. A hulking commander announced that his unit had apprehended a local separatist in a nearby forest. “The unit operating here was local,” the commander explained. “They knew the forest routes when they needed them.”