Brazil began deploying some 30,000 troops Saturday to secure its borders as it prepares to host the World Cup that kicks off next month.
The operation involving the army, navy and air force will extend over the 16,886-kilometer (10,492 miles) frontier separating the South American giant from its 10 neighbors.
The internationally coordinated effort is part of a strategic border security plan announced by President Dilma Rousseff in June 2011.
"It is the single largest mobilization carried out by the state to combat illegal activity from the north to the south of the country," the government said in a statement.
A similar security operation took place ahead of last year's Confederations Cup, widely regarded as a test run for the World Cup extravaganza that will see football games held in 12 cities.
Among other crimes, the operation will target drug and arms trafficking, as well as illegal immigration. It will also provide medical care for needy communities.
The Defense Ministry has not specified how long it will last, with a spokesman telling AFP that the military doesn't want to "give advance warning to criminals."
Brazil shares borders with Argentina, Bolivia, Colombia, Guyana, Paraguay, Peru, Suriname, Uruguay, Venezuela and French Guiana. More than half of these zones pass through rivers, lakes and other waterways.
The FIFA World Cup runs from June 12 to July 13. Brazil expects to welcome more than 600,000 foreign tourists for the massive event, as well as the internal displacement of more than three million locals.