What it means:
the horrors of war
How Shakespeare used it:
In Julius Caesar, Act 3, Scene 1, a grief-stricken Mark Antony predicts that the instability following Caesar's murder will result in civil war: "Cry 'havoc!' And let slip the dogs of war!"
("Cry havoc" was the military order for soldiers to seize plunder from an enemy.)
"If you doubt that Obama is about to let slip the dogs of war, you need only look back at what he said as a long-shot presidential hopeful in a controversial August 2007 foreign policy speech." James Gordon Meek, New York Daily News, May 10, 2010
Dogs of War has also been used in the titles of songs, video games, novels, and films.