Sisu is a Finnish film, not from Quentin Tarantino but certainly cut from the same variety of gruesome cloth. The film is visceral and over the top, celebrating slaughter, in a variety of horrifically novel, ways.
I personally found the whole affair gratuitous, to be honest. What dwelt at the back of my mind and I feel should be remembered, is war is not a joke or a carnival.
I grew up surrounded by people who lived and in some cases, served during WWII. The few tales they told were sad, often tragic and spoke of people trapped into a reality, not of their making or their wanting.
On the upside, Sisu is well paced, exposition driven and has lots of variety in its action. Acting is solid but exposition, is really this flicks, true driver. On a certain level too, this film, recalls spaghetti Westerns, with a WWII, make over.
In summary, if you like splatter style films, you'll probably like this, Just keep in mind, real people lived and died in WWII, on both sides. War is not a game, its not an entertainment.