While Ukraine has successfully reclaimed huge swathes of territory in the country’s east in recent months, U.S. officials expect the onset of winter will slow the pace of fighting as both the Russian and Ukrainian armed forces contend with muddy terrain, lack of ground cover, and a morale-sapping bitter cold. 

The region’s icy winters have played to Moscow’s advantage in the past, helping to arrest advances by Napoleon and Adolf Hitler’s under-prepared forces, earning the nickname “General Frost” or “General Winter.” But in Ukraine, Moscow faces an adversary acclimatized to the winter conditions, while analysts expect the cold will help—and hinder—the two militaries in different ways. 

“I think the main difference is that Ukrainian troops are better equipped to deal with the conditions,” said Michael Kofman, an expert on the Russian military with the Virginia-based think tank CNA. “But Ukraine is likely to have the more difficult task of pursuing offensive operations, whereas the Russian military seems largely set to defend.”

From the outset of the war, Ukraine has received military and humanitarian aid from a phalanx of Western countries that has left its troops significantly better equipped to weather the chilly months ahead. In October, Canada announced that it was to send nearly half a million items of cold-weather gear, while the latest military aid package from Washington included 200 generators for Ukrainian troops.

The Russian military has been beset by logistics challenges since the beginning of the war. Russian officials have acknowledged that they didn’t have adequate gear to equip the hundreds of thousands of troops called up in a partial mobilization announced in September, which is likely to compound the failing morale of Russian troops as the mercury dips.