Sam Mendes’s World War I drama, 1917, brings The Great War to modern audiences with raw ferocity. It makes no attempt to entertain, preach, tear-jerk, or inspire. It provides little context, but brings powerful lessons from the past from a war largely eclipsed by the Second World War and the passage of more than a century. The film centers entirely on two lance corporals, Blake and Schofield, commissioned to deliver a message to Colonel MacKenzie (Benedict Cumberbatch) of the 2nd Battalion of the Devonshire Regiment. The message orders MacKenzie to stand down, because his 1,600 men—one of them Blake’s brother—are walking into a trap.  In a continual shot, Mendes takes…