BERLIN>> After incremental gains for months, Russian forces are advancing on Ukrainian battlefields at the fastest pace this year. They are bombarding Ukrainian cities with some of the biggest drone and missile strikes of the war. They have even opened another front in northern Ukraine.

The Kremlin’s summer offensive appears to be underway.

Military analysts say it is clear that Russian forces this month began their latest concerted attempt to achieve a breakthrough, even as Moscow’s representatives have engaged in the first direct peace talks with Ukraine since 2022.

In particular, Russian forces are pushing into the remaining Ukrainian-controlled territory in the Donbas area in the east, in the fourth year of a conflict that has been a war of attrition. They used the winter lull to build up equipment reserves, improve battlefield communications and tweak the tactics and technical abilities of attack drones, the military analysts said.

Despite some localized battlefield successes, the pace of Russia’s advances remains slow, and few analysts expect it to achieve a decisive victory this summer that would reshape the war.

Russia’s intensified bombing campaign and mounting civilian casualties are hurting geopolitically. President Donald Trump has stopped praising President Vladimir Putin of Russia and threatened new U.S. sanctions against Russia. Ukraine is deepening its alliance with major European nations. And the Ukrainian public is more skeptical than ever of Russia’s peace overtures.

“What Vladimir Putin doesn’t realize is that if it weren’t for me, lots of really bad things would have already happened to Russia, and I mean REALLY BAD,” Trump said in a social media post Tuesday. “He’s playing with fire!”

The Kremlin, in typical fashion, has not directly commented on the offensive or announced its commencement. Putin has said merely that the Russian forces are creating a “buffer zone” with Ukraine to protect Russian civilians from enemy raids. He also has repeated his mantra that the war will end only when Russia eliminates the “root causes” of the conflict, a shorthand for wide-ranging demands that Ukraine and its allies see as subjugation.

While advancing on the ground despite heavy losses on both sides, Russia also is using combined drone and missile strikes to overwhelm Ukrainian air defenses, exhaust its citizens and deplete its industrial base.

Russia’s defense ministry has justified attacks on Ukrainian cities as a tit-for-tat response to the more limited Ukrainian drone strikes on Russian towns and cities, which are causing a smaller number of civilian deaths.

It is unclear what role the Kremlin expects the unfolding offensive to play in the broader complex diplomatic maneuvers over ending the war. Nor is it clear whether Trump would follow through on his threats to exert more pressure on Putin to reach a ceasefire.

Some Western analysts say Putin may be using the dry weather season most conducive for offensive operations to maximize his negotiating power before giving more weight to peace talks later this year. It would be rational, they argue, for Russia, which has had the edge on the battlefield for most of the past two years, to use military pressure as leverage in any negotiations.

“Russia is used to the idea of fighting and talking at the same time,” said Samuel Charap, a Washington-based senior political scientist focused on Russia at Rand Corp., a security research organization. The offensive, he said, shows that Russia is unwilling to meet European and Ukrainian calls for a ceasefire before negotiating a peace deal that satisfies its demands.

Charap does not expect a diplomatic breakthrough in the near future, given how far apart the two sides are. But he said the current uptick in violence did not rule out progress in talks.

Warring sides often “attempt to get as much as possible before the guns fall silent,” Charap added.

But many other analysts, as well as the governments of Ukraine and the European Union, say the acceleration of attacks prove that Putin is not serious about the peace talks, which tentatively restarted in Istanbul this month under pressure from the White House. The Russian offensive is not about gaining negotiating leverage, they say — it is about winning the war.

On Wednesday, Russia’s foreign minister, Sergey Lavrov, proposed a new round of talks in Istanbul on Monday. Ukraine’s defense minister, Rustem Umerov, responded by saying that Kyiv was open to another meeting but wanted to see concrete ceasefire proposals from the Kremlin first. Kyiv said it had submitted its own proposals to allies.

“Diplomacy cannot succeed amid constant attacks,” President Volodymyr Zelenskyy of Ukraine said Monday, hours after one of Russia’s largest aerial strikes of the war.

Some Russian analysts tied to the opposition contend that this year’s offensive could backfire, the culmination of Putin’s military hubris. They argue that any Russian gains might evaporate as the country’s military machine deflates this year under economic pressure and dwindling resources. But Russia’s military and economy have survived multiple setbacks and predictions of collapse.

For now, Russian forces are on the attack.

This month, they have more than doubled the area that they seized in April, capturing an average of 5.5 square miles each day, according to data from Deepstate, a Ukrainian war-monitoring group with ties to the country’s military. Russia this month is advancing at the fastest pace since November, the data shows.

Most of the recent gains came in Donetsk, one of the two regions that make up the Donbas, the historically Russian-speaking area at the center of the Kremlin’s territorial claims. This month, the Russian military broke through defenses between the besieged Ukrainian cities of Pokrovsk and Toretsk, pushing north toward the last regional logistical hubs under Ukrainian control.

The attack appears to be the beginning of a planned Russian campaign to conquer the remainder of Donetsk this year, said Dmitri Kuznets, a military analyst at independent Russian news outlet Meduza.

Russian forces also are making smaller gains in the Sumy region, north of Kharkiv. They are building on the momentum after pushing back most Ukrainian forces that last year had occupied part of Russia’s Kursk region, across the border from Sumy.

“A decision has been taken to create the necessary security buffer zone along the borders,” Putin told his ministers in a televised meeting last week. “Our armed forces are working on this task right now.”

Most military analysts believe that Russia lacks the resources to occupy all Ukrainian land bordering Russia. But the Sumy incursion, they say, has succeeded in tying down thousands of Ukrainian soldiers, limiting Ukraine’s ability to reinforce its fraying defenses in the Donbas.

Russia also appears to have expanded the production and improved the effectiveness of its drones. Last week, Russian forces launched hundreds of drones and missiles at Ukrainian cities over three nights, the biggest barrage of the war.

A small but significant fraction of these weapons are penetrating air defenses and causing damage to industrial and civilian buildings. Military analysts have attributed this trend to a combination of Kyiv’s dwindling anti-air ammunition, innovations in Russian tactics and the sheer scale of the attacks.

In particular, Kuznets said, Russia has been able to upgrade the motors on some of the domestically made models of the Iranian Shahed drone. The new motor allows those drones, known in Russia as Geran, to carry bigger payloads and fly at higher altitudes, making it harder to shoot them down or jam their signals.

On the night of May 24-25, for example, Russia launched 367 drones and missiles at Kyiv, according to the Ukrainian air force. The air force said that 56 got through its defenses, including all nine Iskander ballistic missiles launched that night.

Twelve civilians died in that attack, according to Ukrainian officials. The United Nations reported a rise in civilian war casualties in Ukraine even before this month’s record barrages — more than 200 civilians killed in April, the highest figure since September of last year.