After a pivotal period in Ukraine, U.S. officials predict war's path

That time has passed, and officials say the picture is increasingly clear: Russia is likely to end up with more territory, they said, but neither side will gain full control of the region as a depleted Russian military faces an opponent armed with increasingly sophisticated weapons.

While Russia has seized territory in the easternmost region of Luhansk, its progress has been plodding. Meanwhile, the arrival of American long-range artillery systems, and Ukrainians trained on how to use them, should help Ukraine in the battles to come, said Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff.

“If they use it properly, practically, then they’re going to have very, very good effects on the battlefield,” General Milley told reporters traveling home with him this month after visiting Europe.

Pentagon officials said that meant Russia might not be able to make similar gains in neighboring Donetsk, which along with Luhansk forms the mineral-rich region of Donbas. Ukrainian troops have been battling Russian-backed separatists in Donbas since 2014, when Moscow annexed Crimea from Ukraine.