By Steve Olafson

OKLAHOMA CITY (Reuters) - Mighty forces are gathering in the northeast corner of Oklahoma, and they're itching for a fight. They're well-organized, high-spirited and heavily armed -- with paintball guns.

In one of the largest paintball games in the world, some 3,000 people will relive the events of June 6, 1944, D-Day, when German-occupied France was invaded by Allied Forces, marking a turning point in World War II.

This year's Oklahoma version will mark the 14th time a D-Day-style paintball game has been staged. There's an Allied side and a German side, of course, and even the French Resistance is represented, but it's not just a paintball free-for-all.

Instead, in a rugged, 800-acre park, Allied Forces and the Third Reich will compete to achieve certain goals based on the many individual battles that occurred 67 years ago.

There are mock tanks rumbling around, pyrotechnics exploding and soldiers tumbling out of plywood landing craft amid a cacophony of clacking paintball guns.

"The field sorts out the men from the boys," said Andy Van Der Plaats, a 64-year-old marketing consultant from North Fort Myers, Fla., and a high-ranking officer in the Allied paintball chain of command. "The adrenalin is just cranked. It's stressful."

It's a big deal in Wyandotte, population 500, where Dwayne Convirs created the event in 1997 to honor his grandfather, Enos Armstrong, a combat engineer who fought his way through Europe after landing in Normandy on D-Day.

The first version of Oklahoma D-Day drew 135 players, Convirs said. Since then as many as 15,000 people - including the families of players -- have shown up to either camp out on the grounds of Oklahoma D-Day Adventure Park or stay in nearby motels.

"This is their vacation," Convirs, 46, told Reuters. "It's not really about the game, it's about the event."

The big D-Day paintball battle takes place this year on June 11 after a week of preliminary activities including a flag-raising ceremony, a parade, military-style chapel services, and evening showings of movies such as "Patton," "The Longest Day" and "Band of Brothers."

At Oklahoma D-Day, the outcome is definitely not guaranteed. The Axis side has won the past three years.

While the ultimate result may not always match history, pains are taken to recreate certain historical missions, such as the capture and defense of bridges, churches, crossroads and towns. And all the while, thousands of paintballs are flying through the air; if you're hit, you have to sit out awhile in a "dead zone."

The game is taken seriously by those who spend $100 to play and a tidy sum to buy gear, including paintball guns, which can cost anywhere from a few hundred bucks to several thousand dollars.

REVERENCE

Despite the fun-and-games atmosphere in Oklahoma, there is a palpable undercurrent of patriotism and reverence for those who fought the real fight on D-Day.

For the past two years, Jake McNiece, 92, a D-Day paratrooper who is a member of the Oklahoma Military Hall of Fame, has been a guest at the D-Day paintball games. He's going back this year.

McNiece, who lives in Ponca City, Oklahoma, is dismayed how little young people know about World War Two. The Oklahoma D-Day event, he said, keeps the history alive.

Blind in one eye and deaf in one ear, McNiece is not shy about telling stories of his own experiences, whether it was when he parachuted into Normandy to blow up a bridge before the Allied troops came ashore or when he parachuted into Bastogne during the Battle of the Bulge.

"We don't brag about it and we don't apologize for it," he said. "War is hell. It's a killing game."

He talks to the participants, young and old, and, with his wife, Martha, sells copies of his book, "The Filthy 13," which details his experiences with the 101st Airborne Division.

"It's unbelievable the amount of respect he gets, especially from young people," Van Der Plaats, the Florida marketing consultant, told Reuters.

Even though it's just paintballs being fired, the tactical maneuvering, frequently uphill if you're on the Allied side, is physically taxing in the summer heat, Van Der Plaats said.

Meanwhile, there's a cat-and-mouse game of strategy going on.

Both sides are known to use scanners to intercept the radio communications of their foe and aircraft have been employed to determine the enemy's positions, Van Der Plaats said.

Finally, if it all gets too intense for the paintballers, there is a "chaplain" available to talk it over.

Overseeing this with a certain amount of amazement is Convirs, who remembers the event's humble beginnings and the stories of his grandfather, who helped build 200 bridges in Europe, usually while under fire from the Germans.

"We try to make it patriotic and make people think about life," he added. "There's a lot of people who gave their lives for us to have freedom. A lot of people forget that."

(Editing by Corrie MacLaggan and Jerry Norton)