During WWII, twelve soldiers are offered commuted sentences if they can survive a suicide mission behind enemy lines.
This is a genre that used to produce some of the best action movies of all time (this, The Wild Bunch, half the good Shaw Brothers films, Aliens), and which Hollywood has relentlessly been trying to revive, with the results ranging in quality from Suicide Squad to Rogue One. What that says about the modern world is beyond me.
Anyway, this is one of the top action films of all time, and the cast is unbelievable. Go watch this.