A Ukrainian serviceman peers out of a tank in the Donetsk region, where Russia has seized towns. The war in Ukraine has turned into a grinding artillery contest where Russia is steadily gaining ground thanks to its overwhelming advantage in firepower . As the U.S. and allies gather Wednesday to discuss fresh military aid to Kyiv, Ukraine’s fate will largely depend on how fast and in what quantities these heavy weapons arrive. Without a broad and rapid increase in military assistance, Ukraine faces a defeat in the eastern Donbas region , Ukrainian officials warn. That would pave the way for Russia to pursue its offensive to Odessa and Kharkiv after regrouping in coming months, they say, and potentially all the way back to the capital, Kyiv, after that.