You are right about the World Bank allowing the developiing countries to borrow more money to cover their existing debt. I think that once southern countries build up large external debts, as most have, they cannot get credit or cash anywhere else and are forced to go to these international institutions and accept whatever conditions are demanded of them. I don't think any of the countries have emerged from their debt problems and most countries now have much higher levels of debt than when they first accepted IMF and World Bank assistance.
Given the situation that you laid out above, what explains the borrowing and lending? What interests are behind the practice? Who benefits aside from "thiefs?"