Mel Gibson on set of Hacksaw RidgeLOS ANGELES, July 29 (UPI) -- In the trailer for the upcoming Mel Gibson-directed Hacksaw Ridge, Andrew Garfield stars as Desmond Doss, a conscientious objector who refused to fight during the Battle of Okinawa.Based on a true story, Doss -- a Seventh Day Adventist -- refused to fire a weapon during the Battle of Okinawa in World War II. Instead he single-handedly saved the lives of 75...