In October 2000, Klitschko won the WBO belt on points 120-106, 119-107 and 118-108 _ a near shutout in boxing _ and Byrd left the ring with one eye shut due to the 2-meter (6-foot-7) Ukrainian's powerful jab.
But Byrd, 35, who is 14 centimeters shorter (5 1/2 inches), said he had since learned how to combat big fighters during his eight straight wins over the likes of Evander Holyfield, David Tua and Jameel McCline.
"Nobody beats me twice," said Byrd. "Five years ago, I was more of a finesse fighter. I was willing to fight anybody, but at the same time I was timid of the bigger guys. I do not fear anybody anymore as far as taking their shot."
However, the reputation of Klitschko (45-3, 40 knockouts) as one of the sport's best young heavyweights was badly damaged after being knocked out by Corrie Sanders and Lamon Brewster.
In September, he rose from the canvas three times to win a unanimous decision against the favored Nigerian Samuel Peter and revive his career, but Klitschko knows that doubts about him remain.
"The man without a chin, no stamina, dead man, broken man, whatever," Klitschko said. "On your way to the top, you always get some criticism. Criticism is a great motivation. Failure is not an option to me."
All 14,500 tickets for the fight at the SAP Arena in Mannheim, Germany, were sold within hours. Klitschko and older brother Vitali, the retired WBC champion, are still hugely popular in the country where they launched their careers.
Klitschko believes experience has made Byrd (39-2-1, 20 knockouts) a better boxer than five years ago. The American readily agrees, especially when it comes to fighting a big opponent.
"I think I am more confident now in my ability to fight bigger, taller guys," Byrd said. "I just want to show I am the best out there. I am going to beat him."
At 95 kilograms (210 pounds), the former middleweight Byrd will give up around 14 kilograms (30 pounds) to Klitschko. He will also face a hostile crowd.
But Byrd knows how fast that can change after beating Vitali Klitschko in another David vs. Goliath bout in Germany in April 2000.
"They did not accept me when I got in the ring, but after four or five rounds they saw this little guy in there fighting hard and putting up a pretty good fight, and they were cheering for both of us," Byrd said, reports AP.
The Russian military have already achieved significant success in the demilitarization of the Armed Forces of Ukraine