Russian troops are making steady progress in Ukraine's east on the back of more-concentrated artillery and air power, now controlling almost all of the Luhansk region and threatening to encircle thousands of Ukraine's most experienced troops.
That is sparking fears that Russia could be poised for a bigger breakthrough, and leading to increasingly panicked calls from Kyiv for even more powerful offensive weapons.
Russia's capture of a series of towns including Popasna means its forces hold 95% of the Luhansk region that makes up the northern half of the Donbas area. On Friday, Ukraine's military command said Russian troops were pushing on from Popasna toward the town of Bakhmut, 32 kilometers (20 miles) west, seeking to isolate Ukrainian forces in a pocket of government-held territory around Sievierodonetsk.
UK Prime Minister Boris Johnson described the Russian gains as "slow, but I'm afraid palpable, progress," in a Bloomberg interview. He also backed Ukrainian demands for supplies of longer range multiple launch rocket, or MLRS, systems as "where the world needs to go."
The recent Russian gains appear at least in part to be the products of past Ukrainian success. By mounting so effective a defense that Russian commanders had to withdraw from around the country's two largest cities – Kyiv and Kharkiv – Ukraine also drove them to abandon a wildly over-ambitious battle plan that had left their troops thinly spread and too far from logistical lifelines.
Ukrainian military spokesman Oleksandr Motuzyanyk described the change in the Russian approach to the war as "colossal" at a briefing this week. Russian commanders now take fewer risks and ensure better air cover as they pursue scorched earth tactics. That increasingly entails leveling Ukrainian defenses with extended artillery barrages before attempting to secure territory.
President Volodymyr Zelenskiy in a Friday night video address called the situation in Donbas "very difficult," adding "the occupiers are trying to achieve in at least a hundred days of war the goals they hoped to achieve in the first days after February 24."
Moscow has attempted to remedy some of the challenges it faced in "logistics and sustainment," which left troops without crucial supplies in the early days of the war, Pentagon spokesman John Kirby told reporters on Friday. Part of the improvement stems from the fact Donbas is closer to Russia and part comes from a higher degree of caution about "getting too far ahead," he said.
A sense that the tide of the war could be turning in favor of the likely narrowed goals of President Vladimir Putin comes as some, including former US Secretary of State Henry Kissinger, call for Ukraine to consider trading territory for a cease-fire.
Yet how to interpret the Russian advances has sharply divided military analysts, with many warning against drawing conclusions from incremental movements on a relatively small part of the battlefield that earlier this month saw Russia suffer major losses in a failed attempt to cross the Siverskyi Donets river.
Just as previous Russian setbacks led to an over-optimistic consensus on Ukraine's ability to win the war, relatively minor gains are now driving the kind of pessimism reflected in Kissinger's remarks, Lawrence Freedman, Emeritus Professor of War Studies at King's College London, wrote in a Friday blog post.
"This indicates the ever-present danger for those analyzing the course of this war of getting too far ahead of events on the ground," Freedman wrote. "The best assessment of Russian strategy now is that it seeks to take what it can from the current effort and then dare Ukraine to try to seize it back."
So far Ukrainian commanders have not taken that bait, either because they are building up reserves and awaiting the arms needed from the US and other allies to make a successful counter-offensive possible, or because they are themselves suffering heavy losses and cannot.
In the longer term, the arrival of ever more powerful weapons and fresh Ukrainian volunteers, combined with the steady attrition of Russian forces and equipment, suggests the slow pace of movement on the battlefield favors Ukraine, according to a weekly update by Rochan Consulting, a Warsaw-based group that closely follows the war.
"Time is working in Ukraine's favor," Rochan said in the report. "Unless Russia conducts mobilization (general or partial), its armed forces will not only stall over the next few weeks, but the influx of Western weaponry and Ukrainian personnel will allow Kyiv to start pushing Russian units back along a much broader front."
In Moscow, Security Council Secretary Nikolai Patrushev said this week that Russia had no deadlines to meet in pursuing its "special military operation" in Ukraine.
Yet there are dangers for Zelenskiy's government, even from the limited win that Russia's capture of the Sievierodonetsk pocket would represent for Putin, according to Mykola Bielieskov, a military analyst at Ukraine's National Institute for Strategic Studies, a government think tank.
With Russian artillery now in reach of supply roads to the pocket, Ukraine's commanders face difficult choices: To bring in reinforcements under fire, to withdraw under fire, or mount a Mariupol-style defense after encirclement, in the hope that a counter-offensive and relief will come in time.
"All options are militarily and politically risky," Bielieskov said, speaking by phone from Kyiv. "It's very difficult to explain to Ukrainians why the Russians still have the ability to move forward, after being rolled back from Kyiv and Kharkiv. So even if it is not a major success, this local success would have negative repercussions for the government."
Bielieskov blamed the slowness of even the US administration to make the move from giving Ukraine's soldiers what they need to survive Russian attacks, to giving them what's required to compete with Russia's quantitative advantage in artillery and mount counter-offensives.
Rather than the 90 howitzers the US has promised to date, Ukraine needs 400 to 500, as well as MLRS with ranges of at least 70 to 80 kilometers, weapons that will allow it to damage Russian forces and firepower at depth, according to Bielieskov.
Yet despite Johnson's support and a CNN report that the US is preparing to green light sending MLRS to Ukraine, the administration in Washington has been hesitant, worrying that the missiles - some of which have a range of 300 kilometers - might be used to strike deep inside Russia, according to CNN and others.
A senior defense department official said Thursday that no decision had been taken, meaning even if the US goes ahead it would be weeks before any of the systems appear on the front lines.
"Washington decided that Russia will not be allowed to prevail militarily, but it is doing that in a piecemeal fashion and there remains no consensus to deliver enough weapons, quickly enough to turn Ukraine's defense to offense," said Bielieskov. "Remember that although the Russians are being bled, so are we."
— With assistance by Daryna Krasnolutska
Disclaimer: This article first appeared on Bloomberg, and is published by special syndication arrangement.