The occupation of Rocinha, a notorious hillside "favela" that overlooks some of Rio's swankiest areas, is a crucial part of the city's preparations to host soccer's World Cup in 2014 and the Olympics two years later.

Security forces have occupied nearly 20 slums in the past three years but none as symbolically or strategically important as Rocinha, a sprawl of shacks, stores and evangelical churches located at a traffic choke point between the main city and western areas where most Olympic events will be held.

With large army helicopters thudding overhead, soldiers and police began climbing the slum's winding roads just after 4 a.m. and declared the operation a success within two hours after encountering no resistance.

The invasion of Rocinha and the nearby Vidigal slum was as much a media event as a military operation, as dozens of reporters followed police up through deserted, garbage-strewn streets. The authorities had announced their plans days in advance, giving gang members plenty of notice to flee.