Declaration Of War, trained by Aidan O'Brien and ridden by Joseph O'Brien, won the Queen Anne Stakes, the opening race of Royal Ascot 2013.
American superstar Animal Kingdom was one of the first beaten.
The Kentucky Derby and Dubai World Cup hero was a hot favourite for this one-mile Group One contest, but with the early pace far from frenetic, Graham Motion's challenger was pulling fiercely for his head under John Velazquez, who had a distinct lack of cover.
When the five-year-old did come under pressure from the halfway stage, there was little response and he weakened quickly to finish in arrears.
Declaration Of War, always held in high regard by trainer Aidan O'Brien, was a 15-2 chance to bounce back from a disappointing run when favourite for the Lockinge Stakes at Newbury last month.
Always travelling strongly in the hands of the trainer's son Joseph, the four-year-old was briefly stuck behind a wall of horses and it appeared the gap would never come.
However, once in the clear, Declaration Of War showed brilliant acceleration and was well on top in the end.
The War Front colt passed the post three-quarters of a length clear of Aljamaaheer, with Gregorian third.