By Pavel Polityuk and Natalia Zinets KYIV (Reuters) – Ukraine said on Thursday it had been forced to cede some territory in the east of the country in the face of a Russian offensive, and the head of the NATO military alliance said Moscow must not be allowed to win the war. Ukrainian President Volodymyr Zelenskiy this week described the pressure his armed forces were under in the Donbas region in eastern Ukraine as “Hell”. He spoke of fierce fighting around the town of Avdiivka and the fortified village of Pisky, where Kyiv has acknowledged its Russian foe’s “partial success” in recent days. T…