The movie is based on a brilliant and realistic book (Unknown soldier) about the "Continuation War" between Finland and Soviet Union from 1941 to 1944.
After the initial fast attack phase the war turns into sleepy trench warfare (1942-44), then (1944)the company has to retreat and finally stop the storming Red Army forces. There exists a wide spectrum of characters from cowards to heroes, from peasant rank-and-file soldiers to cocky officers. The scale in personalities and changing situations of war, which are credibly described, makes the movie a spectacle.
It helps a lot if one knows some of the underlying history, but the story is rather universal tale of the cruelty of war and the men who have to live and die for their country and different motives. The language with dialects is versatile, but in Finnish only. This old version (1955) is in my opinion better than the later one (1985).