The Ukrainian military's routing of Russian forces over the past week has highlighted both the fighting capabilities of Ukraine's military and the effectiveness of the Western military aid provided to date.
Outgunned several times over by most estimates, Ukraine leveraged Western artillery and rockets to plow through what has been considered the world's second-most-powerful military, recapturing dozens of towns, including key junctures.
With many leaders and analysts in Washington and Brussels convinced the West's own security is on the line in this war, Ukraine's surprising success would seem to give the United States and Europe fresh impetus to accelerate military aid shipments to Kyiv.
Yet, Washington analysts and lobbyists say that little is likely to change in the short term -- largely because of persistent fears of provoking a Russian escalation. Kyiv's success could even stymie efforts to supply more powerful weapons and ammunition, such as guided missiles with a range of 300 kilometers, they say.
"The same cautious tendencies we've seen in the Biden administration and, of course, even more in European capitals like Berlin and Paris, continue," John Herbst, the former U.S. ambassador to Ukraine in 2003-06 who is now the senior director of the Atlantic Council's Eurasia Center, told RFE/RL following a recent trip to Kyiv.
"I have no doubt that some of the 'less resolute voices' in all those places will point to this success as a reason to explain why Ukraine does not need more aid."
Aid to Ukraine was a contentious issue among Western states and their citizens even before Russia's February 24 invasion.
As Moscow massed combat-ready troops on Ukraine's border at the end of 2021 and war looked imminent, Western countries largely rejected Kyiv's requests for weapons for fear that providing lethal aid could provoke the Kremlin.
Even after Russian President Vladimir Putin launched his large-scale invasion, Western governments initially withheld military aid amid expectations Moscow would quickly capture Kyiv, experts say.
However, as Ukraine fought off Russia's initial lightning attack and it became clear that the contest would not be as one-sided as many expected, the first tranches of Western aid began arriving. The United States and Europe have continued to send aid -- albeit slowly, according to Ukraine supporters -- with more powerful and sophisticated weapons added to the mix.
However, the West has also imposed some limitations on the use of those weapons, such as a ban on striking targets inside Russia.
"The nature and level of support from the United States, and to some extent Europe, is a direct function of the effectiveness of the Ukrainians militarily on the ground," said Daniel Vajdich, president of the Washington-based lobbying firm Yorktown Solutions, who advocates on behalf of Ukraine.
Ukraine's ability to slow the advance of a more powerful army and then push it back "allows advocates both inside and outside of the government to say: 'Look, what we're providing them is working. Imagine [what would happen] if we provided them a little bit more,'" Vajdich said.
However, the lobbyist says he does not see greater U.S. military aid immediately flowing to Ukraine on the back of its successful counteroffensive, but that could change with time. "I do think that this [success] is going to put pressure on folks to deliver the Ukrainians more of what they need over the medium term -- weapons with more advanced capabilities -- because they are proving that they can use it, can use it effectively, and that it makes a difference," he said.
During the first months of the war, as the United States contemplated sending Ukraine more powerful weapons, there were debates in Western government and academic circles about the ability of Ukrainian forces to quickly learn to use NATO weapons and even whether they would have much impact against a bigger military.
This month's successful counteroffensive has answered those questions.
To further extend the gains of recent days and ultimately drive Russia from Ukraine, Herbst says Kyiv needs longer-range artillery and missiles, fighter jets, tanks, and more modern armored personnel carriers, among other items.
Ukraine's repeated requests for ATACM guided missiles that can strike targets up to 300 kilometers away have so far gone unanswered.
While Herbst says U.S. military aid to Ukraine has grown stronger over time, it has done so at a slow pace, reflecting the "persistent caution" inside the administration of U.S. President Joe Biden about triggering escalation by Russia. "We have yet to see a change in the pattern -- a speeding up of the pattern," he said.
Over in Europe, Germany -- the European Union's largest economy -- has been criticized for its lack of leadership on aid to Ukraine. Berlin has dragged its feet on sending weapons to Ukraine and has done so in amounts Kyiv regards as small.
During a visit to Berlin earlier this month, Ukrainian Prime Minister Denys Shmyhal pressed German Chancellor Olaf Scholz for additional weapons, including Leopard-2 battle tanks. While Germany has supplied multiple-rocket launchers, self-propelled howitzers, and Gepard anti-aircraft systems, also known as the Cheetah system, it has held back on tanks.
WATCH: RFE/RL joined a Ukrainian Army crew manning a German Panzerhaubitze 2000, a self-propelled, long-range howitzer, as it opened fire on Russian positions.
Even after Ukraine's breakthrough this month in the east, German Defense Minister Christine Lambrecht again rejected Kyiv's request for tanks. "No country has delivered Western-built infantry fighting vehicles or main battle tanks so far," she said in Berlin on September 12. "We have agreed with our partners that Germany will not take such action unilaterally."
There are influential voices in Germany pushing for a more aggressive policy in the light of Ukraine's battlefield successes. "Certainly, this is not the time for dithering and hesitation," Marie-Agnes Strack-Zimmermann, the chairwoman of the Bundestag's Defense Committee, told dpa on September 11. "The current military advance of the Ukrainian Army and the first recaptured territories in the east of the country speak for Ukraine's fighting strength and unconditional will to take back its invaded country."
In their drive to help Ukraine, Western leaders may also be running up against "Ukraine fatigue," as their constituents tire of the daily news of the war and focus on more immediate issues such as surging inflation and the impact of weaning Europe from its reliance on Russian natural gas.
Greater military aid could be tough to push through in such an environment, experts say.
The United States has authorized $54 billion in military, economic, and humanitarian aid for Ukraine and has sent more than $14.5 billion in weapons from Pentagon stockpiles to the embattled country since the start of the war. The Biden administration is seeking to increase the amount authorized for Ukraine by another $11.7 billion.
"I think there will be donor fatigue at some point," said Mark Cancian, a retired U.S. Marine colonel and a senior adviser at the Washington-based Center for Strategic and International Studies. "It's hard for me to say when that point hits -- when it becomes a real political issue that affects the level of aid, but it will happen," he told RFE/RL.
In the meantime, after seven months of support, the United States and NATO are themselves facing issues with stockpiles of weapons and ammunition.
With the U.S. military having largely been focused on counterterrorism missions over the past two decades, the defense industry curtailed production of the kinds of weapons Ukraine currently needs to fight a heavy-artillery-dominated war of attrition.
Cancian says the United States and its NATO allies are running low on some of the "top of the line" items and will be forced to send older equipment to Ukraine. "We've clearly hit certain levels in certain areas where the military is reluctant to go further because of the risks that might be involved," he said.
He says the United States can source some military aid, such as howitzer ammunition, from allies outside the alliance. "If they do both of those things -- look to older equipment and source globally -- then the West can supply Ukraine indefinitely," Cancian added.
Russia is having the same problems, Cancian says. While Russia probably has enough tanks and planes, Moscow may be running low on missiles, he adds.
Cancian says Ukraine's recent success in the east will help counter any Ukraine fatigue for now and bolster arguments that Ukraine can win if aid is forthcoming.
But, like Herbst and Vajdich, he does not see the United States accelerating that aid on the back of the recent victories. In fact, Ukraine's march toward the Russian border might even "exacerbate concerns" about providing Kyiv with ATACMS, he says.
"I don't think it's going to make a lot of changes to the aid packages," Cancian said.
"I think what it does mean is that the aid packages will continue to flow and that we will continue to provide the same kinds of weapons that we have been providing," he said.