US Army Ranger won the MBNA Chester Vase for Aidan O'Brien but was nearly caught by stablemate Port Douglas.
Favourite for the Investec Derby with some bookmakers before the race, whether he advertised his Classic credentials is up for debate.
Port Douglas attempted to make all under Seamie Heffernan and when US Army Ranger and Ryan Moore swept past the race looked over, but the former rallied to be beaten just a short head by the 4-11 favourite.
Moore said: "He's still very babyish, he travelled really nicely and I just wanted to teach him.
"When he got to the front he had a bit of a look, as the other horse came back he was just going to do enough.
"He's a baby, it's only his second run and he made his debut five weeks ago - he'll learn plenty.
"I was probably a bit too kind to him when he first went there and he's probably switched off on me.
"He didn't know how to fight and he'll learn a lot from that. Aidan's other horse isn't a bad horse, he's a Group Two winner carrying a penalty - they are both decent horses."