Mel Gibson may not always be a good director, but he’s never a stupid one. His Hacksaw Ridge, which premiered here in Venice on Sunday, is blunt and effective, a picture cannily crafted for maximum effect: Whatever subtlety it gets comes from its anchor performance by Andrew Garfield, who plays Desmond T. Doss, a real-life World War II hacksaw ridge away—refused to carry a weapon but whose bravery saved the lives of at least 50 men in his battalion during the Battle of Okinawa.