His nickname "The Greek" came from playing high school football. The team and fans knew his father was of Greek decent. After many years of being called "The Greek", it seems more like his real name than Demetrius.

Demetrius started his training in 1968 under Jerry Wiseman when he was eighteen. His instructor placed a baseball cap sideways on his head and kicked it off. Then he held a board behind his head and broke it with a front snap kick. Young and tough, Demetrius was nevertheless impressed, and his career was underway.

As a brown belt he racked up over a hundred and twenty five victories without a loss. His most memorable brown belt fight was against the undefeated brown belt, Bob Burbridge (Mike Stone and Chuck Norris' students.) This victory was proof of his determination to win. Near the end of 1971 he received his black belt.

Before he committed himself entirely to the emergence of KickBoxing, he racked up win after win on the tournament circuit. In 1974, he won the grand championship at the USKA Grand Nationals. He walked off with the big one at the Texas State Karate Championship for six years in succession. Four times in a row, he beat all comers at the Louisiana State Championships, and he took Allen Steen's U.S. Karate Championships three years back to back. From 1975 on, "The Greek" was totally committed to KickBoxing.

A very muscular five foot five, the Greek perfected an explosive fighting style that consistently enabled him to outpoint men much taller than himself. No doubt partly to compensate for his lack of reach, Havanas took up body building, learning subsequently to punch with astonishing power. By 1980 the Greek had amassed a record of almost fifty fights. Up to that time, only Benny Urquidez had fought more often. Of his nearly fifty fights, Havanas lost only to Benny "The Jet" Urquidez, that fight by only one point. He also lost an unpopular split decision to Earnest Hart Jr. His other defeats were to Chris Gallegos, and Marc Costello - at least one of which losses he later avenged. Beside being a great fighter, Greek was also noted as Texas' best KickBoxing trainer. Training such champions as Billye Jackson, Ray McCallum, Troy Dorsey, Cliff Thomas and Ismael Robles. Greek was fast pounding his way to the doorstep of the elusive world lightweight title.

Then suddenly without notice, the Greek was gone. In July of 1981, while in route to Atlantic City, New Jersey, the Greek was killed in a single engine airplane crash outside Cookeville, Tennessee. With Havanas were D.K. Price, Tony Sandoval and Karen Ruffin.

Three days later an "overflow crowd" spilled out onto the terrace and steps of Restland Memorial Park to attend a one of a kind service for a unique man. A pair of boxing gloves were hung up front, and the Havanas black belt and red satin gi adorned the casket. A photo of the fighter was also visible to mourners. The "Theme from Rocky" was the music with which ceremonies opened. (I Did It) My Way was also playing at the end of the service, during which a personal friend sang "You Are So Beautiful".

Black belts past and present were every where in evidence. Bid Ed Daniel, Skipper Mullins, George Minshew, Jack Hwang, Santae Wilson, Steve Armstrong, Tim Kirby, Billye Jackson and Chuck Norris all came to pay their respects. Pallbearers consisted of Larry Caster, Raymond McCallum, Ismael Robles, Dennis Cox, Phil Wileman and Roy Kurban. After the final prayer, Larry Caster spoke a Korean bowing command while the mourners tendered one last salute to their friend. Though two decades have pasted, the Greek still influences KickBoxing today.