Following World War II and the return of American servicemen to civilian life at home, American motorcycle enthusiasm soared. Many of the returning soldiers missed the rush of life and death experiences from the war. Citing this lack of excitement, veterans snapped up surplus Harley-Davidson motorcycles. Stripping down the motorcycles of all unnecessary parts, riders could squeeze more performance out of the bikes. Clubs sprang up with names like Boozefighters, Pissed Off Bastards and of course the Hell's Angels. Now hold that thought!
"And in this corner.."
Take all that bad-assery, the ruggedness, that concentrated biker image and flush it down the crapper. That's a good start for what the Mods were. They developed around London, along with the Rockers, during the 50's and 60's. For some reason, they adopted scooters for their subculture's transportation. A classic Mod ride was either the Lambretta GT 200 or the Vespa GS 160. Mods tended to be urban middle class. They wore suits with narrow pants and pointed shoes. Come on, a bunch of people riding around on Vespas wearing a suit? Even the Fonz would be beating these people up for shits and giggles. The girl Mods opted for a boyish or unisex look with short cut hair and darkened eyes. Music was also an important part of both subcultures. Mods stuck to American style jazz, soul and blues.
Those Punk Rockers
The rival Rockers were more like the typical badass American biker gang image. They rode modified Triumphs or Nortons with plenty of power for cafe races. Rockers were often manual laborers from rural backgrounds and weren't into much fashion. Their personal decorations extended to black leather jackets (complete with studs and zippers) along with jeans and boots. Rocker music revolved around rock and roll.
To Arms!
Mods and Rockers had their respective turf and hangouts, especially around London. Their polar opposite images lead to squabbles and a general not getting along. Brighton was a frequent spot for the two groups to work out their differences. However, the largest "dispute" arose in the town of Clacton. Mods and Rockers got into a fight and resulted in some property damage ranging from windows to beach huts. The sensationalist media got off their asses to blow the story out of proportion and play up the amount of actual hostilities between the two groups.
The two groups eventually faded out as the flower power movement blossomed in the late 60's. | 
