KYIV, Ukraine — A monthslong border blockade by Polish truckers is starting to have an effect on Ukrainian soldiers in frozen trenches defending against unrelenting Russian assaults, making already fierce battles even more difficult. One Ukrainian soldier, Oleksandr, fighting in eastern Ukraine, said that his unit was still waiting for delivery of two night-vision devices, critical for soldiers navigating their way to fighting positions safely. The equipment has been held up at the border, he sa