Actually in a way when a nations troops are used in a UN peace keeping op they become defacto mercenries anyway. Because the peace keeper's own govt gets paid a fee for every soldier sent. This is why there's always so many 3rd World countries always clamering aboard to get involved in UN peace keeping ops - there's big bicies involved. For example Ghanan peacekeepers in Somalia probably get paid $3 a day or something from their govt, while their govt is actually getting paid $20 an hour or something from the UN for every soldier actually involved in the UN op. So 3rd World govts whose soldiers are earning 3rd World wages make a good profit. Where-as with Western Soldiers on Western wages the amount the govt gets from the UN probably doesn't even match just the wage of each soldier sent, let alone all the added misc & support costs. Also with countries like the US that owe the UN millions, they just have the UN peace keeping op payments deducted from their debt, so they don't get anything back but the good feeling that comes from knowing they are in less debt to the UN.