On paper, Ukraine’s David is running circles around Russia’s Goliath.

In the beginning of the war, Ukrainian defenders worshiped “St. Javelin,” the US-supplied, shoulder-fired, tank-killing missile that turned hundreds of Russian tanks into smoldering hulks of roadside wreckage.

In the current phase of the war, it’s America’s HIMARS shoot-and-scoot precision rocket artillery system that’s helped Ukraine overcome Russia’s numerical advantage by taking out ammunition depots far behind the front lines, forcing Russian guns into hiding to avoid deadly accurate GPS-guided artillery fire.

In more than five months of brutal combat, the plucky Ukrainians repulsed the Russian attempt to capture the capital Kyiv and depose President Volodymyr Zelensky, inflicted morale-busting casualties on Russia’s largely conscription army, and fought the putative superpower to a virtual stalemate in the east, where Russian forces are paying heavily for every few meters they take.

The war is now at a critical inflection point, say outside experts, with only a few months of warm weather before the battle lines are frozen in place and pressure increases on Ukraine’s European allies who rely on Russian gas to keep their people from freezing.

“I don’t want to sound like a character from ‘Game of Thrones’ but, yeah, winter is coming,” said Britain’s top spymaster Richard Moore at the Aspen Security Forum last month.To maintain the flow of military, economic, and political support, Zelensky needs a dramatic battlefield triumph to show the U.S. and the world the war is winnable. 

“It’s important I think to the Ukrainians themselves that they demonstrate their ability to strike back, and I think that will be very important for their continuing high morale,” said Moore. “I also think, to be honest, it will be an important reminder to the rest of Europe that this is a winnable campaign by the Ukrainians because we are about to go into a pretty tough winter.”

Putin seems to be banking on a “winter strategy” that as European countries face higher prices to heat their homes, Western resolve will buckle, and Ukraine will be forced to cut a deal on Moscow’s terms.

But Russian losses have been staggering, with estimates of war dead ranging from 15,000 to 40,000.“We continue to see Russia failing on the battlefield, paying a high price for very little gain, and suffering domestic failures at home,” a senior military official told reporters at a Pentagon briefing. “When you look at the numbers of people that they have lost, it’s impossible to believe that they’re not having to figure out ways to replace them if they want to continue to go toe-to-toe with Ukrainians.”

That said, the Russian president has a high pain threshold, especially because he’s not the one feeling the pain.