According to European and NATO diplomats familiar with the matter, Ukraine’s allies see a two-week window to spirit in heavier weapons like tanks before President Vladimir Putin unleashes an offensive designed to declare some sort of victory by the May 9 anniversary of Nazi Germany’s defeat in World War II. 

Moscow traditionally holds a large annual military parade that day. The Kremlin did not respond to a request for comment on the potential significance of the date in the war timing.

“The next weeks will be decisive,” Josep Borrell, who coordinates European Union foreign policy, said on Wednesday, as the bloc proposed a further 500 million euros ($544 million) to help fund member states’ military aid to Ukraine. That lifts the total to 1.5 billion euros.

The eastern port city of Mariupol has been under siege for weeks and is at risk of falling completely under Russian control within days.

Yet weather conditions, the need to prepare logistics, establish air dominance and reconstitute forces mauled around the Ukrainian capital would argue for a longer time frame to retake the rest of the Donbas region still in Ukrainian hands, according to some diplomats and military analysts.

The trade-off between speed and casualties is one Putin appears to recognize. At a press conference on Tuesday, he said he was often asked if it wasn’t possible to finish the war more quickly. 

“It is possible. It depends on the intensity of military action, and the intensity of military action is unfortunately one way or another linked with losses,” Putin said. “Our task is to achieve the set goals while minimizing losses.”

The Spring mud season

That will be hard to do if Russia throws units into the fight at the height of the Spring mud season, when the ground is too soft and wet for trucks and mobile artillery to move off the roads without getting stuck – something that happened north of Kyiv, leaving some convoys stranded and vulnerable to attack.

That season will end some time in May, but likely not soon enough for any significant campaign win before Putin’s Victory Day parade, according to a Moscow-based military analyst who asked not to be identified discussing sensitive matters. New Russian laws tightly restrict comment and reporting on the war. 

The continued failure of Russian forces to take major towns such as Kharkiv means they can’t use the main Ukrainian highways to move equipment and are forced to send columns of tanks and trucks over much smaller, slower roads. These are better suited for ambush, especially as trees are regaining leaf cover, the analyst said.

Reviving depleted units

Reconstituting depleted Battalion Tactical Groups, which roughly have 600-800 troops and 50 armored vehicles including tanks, will also take time. A Russian regiment typically generates two BTGs for combat and should return to base to regenerate. Some equipment in need of significant repair also has to be moved across Russia.

A T-72 tank, for example, has to be sent to the city of Nizhny Tagil, about 2,200 km (1,367 miles) east of Donetsk, for major repairs, the analyst said. A T-80 tank goes to Omsk in Siberia, 3,000 km away. With the best, most advanced tanks already sent in to fight, any substitutes are likely to be older, less capable models.

“People need to be very careful before talking about a major, large and powerful Russian offensive kicking off soon,” Phillips O’Brien, professor of strategic studies at Scotland’s St. Andrews University, wrote in a recent twitter thread.

All of this is likely to be understood by the Russian campaign’s new commander, General Alexander Dvornikov. 

Although commentary has focused on Dvornikov’s brutal reputation in Syria, he also was in charge of the more successful southern theater of the Ukraine invasion, the likely reason for his promotion, said the Moscow-based military analyst.

Putin’s tactical worry

At the same time there are reasons, beyond the political benefits of a parade, for Putin to want Dvornikov to move quickly.

There is incentive to act before Ukraine can deploy more of its own forces in the east, or take delivery of the hundreds of millions of dollars worth of drones, anti-aircraft, ship and armor weapons, as well as tanks and armored vehicles that the U.S., Britain, Australia and many EU states are now hurrying to Ukraine.

Ukraine has also asked for combat aircraft to ensure it continues to challenge Russian air dominance over much of the country, which has an area larger than mainland France.

Satellites have picked up images of an eight km column of Russian vehicles already heading to Donbas from the north, as well as several columns of tanks and armored personnel carriers moving toward Ukraine from inside Russia, and a nearby air base filling with jets.

Russian losses during the first six weeks of the invasion appear to have been large. While no reliable casualty figure exists in the broad spread between the official Russian data and estimates by Ukraine, a U.S. assumption of about 20% attrition fits with data on verified Russian vehicle losses, according to @OsintTechnical, an open source intelligence outfit.

Twenty percent is a big figure, equivalent to that suffered by the armies serving Confederate General Robert E. Lee, who lost a higher proportion of men than any other general during the American civil war, according to O’Brien, the St. Andrews professor. He sees that as unlikely to change. 

“What it actually is looking at is Russia suffering a constant drip, drip of losses, making small gains, and instead of building up massive force for one effort, feeding forces more slowly over a poor road network. All without air dominance,” O‘Brien tweeted.

High casualty rates alone are unlikely to force an end to the war, given that Russians tend to be more willing than Americans or Europeans to accept them, especially if Putin’s self-described “special military operation” has popular support. Losses can, however, create constraints in critical areas where personnel are difficult to quickly replace, such as combat pilots.

Nor would high casualties stop Putin from declaring victory at any point, given the lock he has on domestic media. The problem, says @OsintTechnical, who uses only the name of his project, is how to stop the war even after Putin has found something to declare as victory. 

“The Russians would still be in Ukraine, so the war would not be over,” he said. “The Ukrainians would just have to try to retake territory.”