The majority came from the poorest parts of Europe - Moldova, Romania and Ukraine - but the main supply route is through Serbia.

BBC: 'Slave trade' thrives in Bosnia

The country's main supply route, a railway connecting Brazzaville and Pointe Noire, the oil-producing town, has been disrupted for the past seven months.

ECONOMIST: Congo-Brazzaville

Twice he made the dangerous journey down the Ho Chi Minh Trail, which was the main military supply route from the North through the Laotian panhandle to the South during the American phase of Vietnam's wars of independence.

CNN: Goodbye to Ho Chi Minh