LOUISVILLE, Ky. — Colonel John’s marching orders are simple: win the Kentucky Derby. Not an easy task, especially with 19 other colts making the same mad dash through the first turn accompanied by the sound of more than 150,000 cheering fans.

As if Colonel John needed another challenge, he’ll be racing on dirt for the first time in Saturday’s 134th Derby.

The Southern California-based colt has never been worse than second in six career starts — all on synthetic tracks made of wax-coated sand, fibers and recycled rubber.

No worries, trainer Eoin Harty says.

“I’ve liked what I’ve seen since I got here and I have no reason to change my opinion,” he said Thursday after Colonel John galloped 1 1/2 miles and got a feel for the starting gate at Churchill Downs by standing in it.

Colonel John is the 4-1 second choice behind 3-1 favorite Big Brown on the morning line.

Co-owner Susan Casner gave Colonel John’s namesake a promotion when she named the colt after longtime family friend Army Reserve Lt. Col. John Geider, a veteran of the Iraq war.

Geider joined Susan Casner to hang Colonel John’s silks signifying their choice of the No. 10 post at Wednesday’s draw. He did a seven-month tour of duty in Iraq in 2005 and now the 52-year-old Dallas resident oversees security and transportation for Kenny Troutt, a racing partner of Casner and her husband Bill.

The Casners, Troutt and his wife had Colonel John buttons and a 28-page color “Official Field Guide” made up to pass out to backstretch supporters of their colt. The booklet includes sections labeled Combat History and Squad Leaders, which naturally are the owners and Harty. The horse even has his own Web site featuring YouTube clips of his races.

Colonel John reflects the Casners’ patriotic support of the U.S. military. They lost their 23-year-old daughter Karri in the 2002 terrorist bombing in Bali, Indonesia. They have another daughter Kayce.

The Casners and Troutts have some Derby experience, even if Colonel John doesn’t. They were part of a group that owned Victory Gallop, who was second in the 1998 Derby and won the Belmont.

Colonel John is Harty’s first Derby horse on his own, but the Ireland-born trainer was Bob Baffert’s top assistant when Silver Charm won in ’97 and Real Quiet did in ’98.

“I truly believe that this horse will be competitive on Derby day,” Harty said. “He’s shown me all the signs that Real Quiet and Silver Charm did.”

Like any good commander, Harty has a strategic vision for Colonel John’s 1 1/4-mile trip under jockey Corey Nakatani.

He sees most of the speed horses positioned on the outside of Colonel John, meaning they’ll need to cross over in front of the field to reach the first turn in front.

“Hopefully we can avoid all that carnage because you know that if those speed horses don’t break as fast as they like and they are hustled to the lead, there might be a logjam,” Harty said. “The race is going to be dictated by what happens on that first turn. I’d like to save some ground and get around that first turn safely.”

Through the backstretch, Harty wants Nakatani to place Colonel John in a stalking position.

“I’d like to be about mid-pack, about seven or eight lengths off the lead, saving some ground and not taking too much dirt in the face,” Harty said.

Then again, the trainer knows Nakatani will need to react to split-second actions by Colonel John’s opponents.

“I have a very good rider and he can call an audible if he needs to,” Harty said. “I’ve got great faith in him and he’s got great confidence in the horse. There’s not much more that I can hope for.”

Except Colonel John’s promotion to the Derby winner’s circle.