A gloomy mood hangs over Ukraine’s soldiers nearly two years after Russia invaded their country. Ukrainian soldiers remain fiercely determined to win, despite a disappointing counteroffensive this summer and signs of wavering financial support from allies. But as winter approaches, they worry that Russia is better equipped for battle and are frustrated about being on the defensive again in a grueling war. Some doubt the judgment of their leaders. Discontent among Ukrainian soldiers — once extremely rare and expressed only in private — is now more common and out in the open. Russia controls about one-fifth of Ukraine, and the two countries are essentially in a stalemate along the front line.