WASHINGTON — Top Biden administration officials say they believe the next four weeks will shape the eventual outcome of Russia’s war in Ukraine, with lasting ramifications that will influence the drawing of the map of Europe for the decades to come.

While officials still expect the war to be long and grueling, they say it is imperative to rush Ukraine with as many new weapons as possible – especially long-range artillery and anti-radar radars. -artillery – to repel the new advance of Russia in the eastern Donbass. Region.

Reflecting the renewed sense of urgency, President Biden announced on Thursday that the United States would send an additional $800 million in military aid to Ukraine, the second such package in just over a week.

Mr Biden said the latest aid package sent “an unequivocal message” to Russian President Vladimir V. Putin: “He will never succeed in dominating and occupying all of Ukraine”.

In remarks at the White House, Mr Biden said that while the United States would announce many details about the weapons it is shipping to Ukraine, some of them would be kept secret. The president borrowed and modified a famous phrase from Theodore Roosevelt, saying the United States would “speak softly and carry a large javelin”, a reference to the anti-tank weapon the Ukrainians used effectively against Russian armour.

Determined to act quickly, Secretary of Defense Lloyd J. Austin III and Gen. Mark A. Milley, Chairman of the Joint Chiefs of Staff, spoke this week with allies around the world and called next month crucial.

If Russia can push east, Mr Putin will be in a better position at home to sell his so-called ‘special military operation’ as a limited success and claim he provided protection for the pro-Russian minority in Ukraine, U.S. officials said. He could then ask for a ceasefire but would be encouraged to use Donbass as leverage in any negotiations, they said. Officials spoke on condition of anonymity to discuss operational matters.

But if Ukraine’s military can stop Russia’s advance into the Donbass, officials say Mr Putin will face a stark choice: commit more combat power to a fight that could drag on for years or negotiate seriously in peace talks.

The first option could mean full national mobilization, officials say, and is politically risky for the Russian leader.

The next phase of the war “will be of crucial importance”, said Peter Maurer, president of the International Committee of the Red Cross, who visited Ukraine in March. “The escalation of hostilities in the Donbass and in all areas affected by the armed conflict is extremely worrying.”

At the Pentagon this week, Mr. Austin and General Milley had non-stop phone calls and meetings with allies centered on one topic: weapons. Mr. Austin spoke with his Romanian counterpart on Monday and with the Spanish Minister of Defense on Tuesday. On Wednesday he met the Polish defense minister, and on Thursday he huddled with his Czech counterpart.

With all four, the discussions were the same, officials said: how to ship more powerful weapons to Ukraine in the coming weeks.

After weeks of focusing on anti-tank and anti-aircraft weapons like Javelins and Stingers, new deliveries last week included long-range artillery, tactical vehicles and mobile radar systems to help Ukrainians detect and destroy Russian artillery positions.

Other countries send tanks, more artillery and anti-ship missiles.

General Milley’s phone log this week looks like a roll call of countries with heavy artillery and weapons: Australia, Britain, Canada, Denmark, France, Germany, Greece, Italy, Netherlands, Norway, Portugal , Sweden and Turkey.

A senior Defense Ministry official has described next month as a crucial turning point for Russia and Ukraine. This phase of the battle ostensibly favors Russia to some extent, as Russian troops move into more open terrain instead of bogged down in towns.

But the official said the Pentagon believed that with the right weapons and the pursuit of high morale and motivation, Ukrainian forces could not only stop the Russian advance, but also repel it.

“The Russians are in a weakened state from which they could recover well given enough time and new draftees,” said Evelyn N. Farkas, the Pentagon’s top policy official for Russia and Ukraine under the Obama administration. , when Russia annexed Crimea. Peninsula. “Therefore, it is paramount to hit them now with whatever we can give the Ukrainians.”

Current and former US military commanders with experience in Ukraine and Europe agree.

“This is decisive for Ukraine insofar as it has to stop the Russian advance to seize all of Donbass,” said Maj. Gen. Michael S. Repass, a retired former commander of the armed forces. ‘US special operations in Europe which has been involved with Ukraine. defense issues since 2016, wrote in an email.

If Mr Putin succeeds in capturing the east and establishing a land corridor to Crimea, General Repass said Moscow would have a stronger position in any negotiated settlement.

“In another month, I foresee exhaustion on both sides with no military decision/outcome either way,” Gen. Repass wrote. “A stalemate means Putin wins, and if Putin ‘wins’, we are in for a bad patch.”

In an attempt to prevent such an outcome, current and former US commanders say the Ukrainian military will seek to disrupt Russia’s military buildup around the eastern city of Izium and other key staging areas with military attacks. long-range artillery and armed drones.

“It’s also about disrupting the Russians while they’re still in replenishment and preparation mode, before they can really get back on their feet,” said Lt. Gen. Frederick B. Hodges, former senior commander of the US Army in Europe. now with the Center for European Policy Analysis.

Even if Moscow reduces its targets and consolidates its army in southern and eastern Ukraine, the outcome of the war remains uncertain at best, military analysts said. Indeed, the underlying weaknesses of the Russian force, which were revealed in the first weeks of the conflict, have not necessarily gone away, they said.

For example, the thousands of Russian reinforcements pouring into Ukraine – including mercenaries, conscripts and troops drawn from Russia’s far east and Georgia – did not train together, analysts said.

Defeated units that have retreated from northern Ukraine will also need time to regroup. Some will be restocked and returned to battle. But others are so damaged that their remaining parts will be assembled into a single new unit, analysts said.

“They don’t have many options to generate new forces if current units face too much attrition,” said Rob Lee, a Russian military specialist at the Foreign Policy Research Institute in Philadelphia and a former U.S. Navy officer. .

“Once this offensive begins in earnest, Russia will face more casualties,” Lee said. “At some point, the attrition will be too great and will limit the ability of the Russian military to effectively conduct offensive operations.”

As Russian forces push into Donbass, they will expand their supply lines and could face the same logistical deficits that plagued them before, officials said.

“We’ll see in the next few weeks how much they’ve learned and how much they’ve corrected,” General Hodges said.

Even if the Russian forces prevail within a month or so, the specter of that army’s advance into western Ukraine or beyond Ukraine’s borders – a real fear at the start of the war – now seems far-fetched, several officials said.

“Win, lose or draw, the Russian military will likely be a depleted force after this next phase,” said Michael Kofman, director of Russia studies at CNA, a research institute in Arlington, Virginia. “Russia would find it difficult to sustain a campaign beyond Donbass.”

But the senior Defense Ministry official warned that for Mr Putin, all of Ukraine – not just Donbass – has always been the ultimate prize.