World War 3 was briefly mentioned in the pages of Justice Society of America #1 and 52.
According to newsarama in week 50 (that’s April 18, 2007) of the comic book 52 World War III will hit. Not only that, but four WWIII one-shots will be released. They are as follows:

WWIII PART ONE: CALL TO ARMS
Writer — Keith Champagne
Penciller — Pat Olliffe
Inker — Drew Geraci
Cover — Ethan Van Sciver

WWIII PART TWO: THE VALIANT
Writer — Keith Champagne
Penciller — Andy Smith
Inker — Ray Snyder
Cover — Ethan Van Sciver

WWIII PART THREE: HELL IS FOR HEROES
Writer — John Ostrander
Penciller — Tom Derenick
Inker — Norm Rapmund
Cover — Ethan Van Sciver

WWIII PART FOUR: UNITED WE STAND
Writer — John Ostrander
Penciller — Jack Judson
Inker — Rodney Ramos
Cover — Ethan Van Sciver

I’m sure a lot of people will accuse DC of ripping off Marvel’s Civil War, however World War 3 sounds as though it is very different. In 52 the war isn’t the main focus, it’s just the climax of what 52 has been building up to, whereas Marvel’s Civil War is the main event.