Of the ethnic gangs that rule America' s inner cities, none has had the impact of the Jamaican posses. Spawned in the ghettos of Kingston as mercenary street-fighters for the island' s politicians, the posses began migrating to the United States in the early 1980s, just in time to catch and ride the crack wave as it engulfed the country. Feared and honored for being " harder than the rest, " they would lay claim to their new American territory with...