Oddly enough the Guardian thinks the Brits are better at this than us "Yank". It is a trend started in earnest when US forces were downsized in the 90s to get the peace dividend. Clinton couldn't field enough troops to do the job in the Balkans (see the Guardian link below) and the US never had enough troops to occupy Iraq. No miscalculation, it was known this was going to be necessary from the beginning.

The privatisation of war -- The Guardian

"It is a trend that has been growing worldwide since the end of the cold war, a booming business which entails replacing soldiers wherever possible with highly paid civilians and hired guns not subject to standard military disciplinary procedures.

"The biggest US military base built since Vietnam, Camp Bondsteel in Kosovo, was constructed and continues to be serviced by private contractors. At Tuzla in northern Bosnia, headquarters for US peacekeepers, everything that can be farmed out to private businesses has been. The bill so far runs to more than $5bn. The contracts include those to the US company ITT, which supplies the armed guards, overwhelmingly US private citizens, at US installations...

"The surge in the use of private companies should not be confused with the traditional use of mercenaries in armed conflicts. The use of mercenaries is outlawed by the Geneva conventions, but no one is accusing the Pentagon, while awarding more than 3,000 contracts to private companies over the past decade, of violating the laws of war."

Let's see, "past decade". That goes back before January of 2001, doesn't it? Halliburton got $1bn (from sole source contract, of course) of what was spent in the Balkans starting in 1995. Google "Halliburton Bosnia Clinton", you'll get some interesting results from authoritative sources.