About the Winter War, did you know that Finnish sniper Simo Häyhä, nicknamed "White Death", was the most successful sniper in the WW2 ? He had 505 confirmed kills. He was severely wounded on March 6, 1940, a bullet hit his jaw and also destroyed his left cheek, but he survived and at the age of 96 in April 2002 ! After the war he was hunter and dog breeder in Finland.
He used different tricks to hide himself like putting snow in his mouth to avoid breathing smoke, compacting the snow before him to avoid it to move when he fired, and he used only normal sights instead of optical sights to avoid light reflection. I've read the soviets even tried artillery bombing to kill him, but it didn't work.
Here he is: