The Iraq occupation—particularly the events in Fallujah and at Abu Ghraib—has introduced Americans to a newly prevalent kind of warrior: private corporate soldiers. Roughly 20,000 of them work alongside the coalition in Iraq—ten times as many per military soldier as served in the 1991 Gulf War. Blackwater USA and other private firms offer services ranging from feeding the troops to armed combat. According to P. W. Singer, the author of Corporate Warriors: The Rise of the Privatized Military Industry, their pay ranges from $250 a month for Kurdish fighters to $1,000 a day for former Green Berets. The growth of these companies over the past decade is attributable to several factors: a trend toward outsourcing in business and government, the overextension of the U.S. military, and the increased frequency of conflict in a post-Cold War world. Here are some notable private contracts from the past decade, ranked by cost.

1. Supplying and training the Saudi National Guard, the elite forces that protect the Saudi monarchy and maintain stability, $831 million for five years (1998): Vinnell Corp.
2. Providing security for the Program Management Office monitoring the reconstruction effort in Iraq, $293 million for three years (2004): Aegis Defense Services. The contract calls for up to 75 two-man security teams trained in "mobile vehicle warfare" and "counter-sniping," and puts Aegis in charge of coordinating all the private security contractors in Iraq.
3. Leading an attempt to overthrow the Nigerian government of General Sani Abacha, $100 million (1998): Executive Outcomes declined the offer. Abacha died of natural causes that same year.
4. Providing a security detail for Afghan President Hamid Karzai, $52 million (2003): DynCorp.
5. Creating a new Iraqi police force, $50 million for the first year (2003): DynCorp.
6. Training a new Iraqi army, $48 million (2003): Vinnell Corp. The contract called for Vinnell to train nine battalions; more than half of the first completed battalion later abandoned the army.
7. Protecting Iraq's oil pipeline, $39.2 million (2003-present): Erinys International. The job requires 14,500 guards.
8. Defending Sierra Leone's capital, repelling an invading rebel army, and storming its stronghold, $35 million (1995-1997): Executive Outcomes. While under contract Executive Outcomes defeated two violent coup attempts by the rebel army. Meanwhile, the firm allowed a quieter internal coup by a third party to succeed; this brought to power a head of state more sympathetic to Executive Outcomes.
9. Providing interrogation services in Iraq, $19.9 million (2003-present): CACI Systems. At least two contractors, one from CACI and one from Titan Corp., have been implicated in the Abu Ghraib scandal.
10. Providing a team of former New Zealand special-ops soldiers to rescue a businessman held hostage in East Timor, $220,000 (2000): Onix International.