A mercenary is also any person who, in any other situation:

The bottom line of the rule of war: "A mercenary, as defined in article 1 of the present Convention, who participates directly in hostilities or in a concerted act of violence, as the case may be, commits an offence for the purposes of the Convention."

Meanwhile, the phenomenon grows, says the Review, which points to a San Francisco Chronicle piece quoting Deborah Avant, a professor of political science and international affairs at George Washington University in Washington, D.C.

"The rate of growth in the security industry is phenomenal," Avant said. "If you had asked a year ago whether there would be 15,000 private security in Iraq, everyone would have said you're nuts. It has moved very quickly over the past decade, but Iraq has escalated it dramatically."

The trend is highly controversial. Some critics point out that security firms are largely unaccountable to governments, the courts or the public.

Some examples:

Steele, the world's fifth-largest security firm, employs around 500 agents in Iraq, about one-third Westerners and the rest Iraqis. As elsewhere – the firm operates in 20 countries – it offers far more than just Hollywood-style firepower. The company's brief includes corporate consulting and high-tech investigations.

Last month Blackwater USA flew a first group of about 60 former commandos, many of whom had trained under the military government of Augusto Pinochet, from Santiago to a 970-hectare training camp in North Carolina.

From there they would be taken to Iraq, where they were expected to stay between six months and a year, the president of Blackwater USA, Gary Jackson, said.

"We scour the ends of the earth to find professionals - the Chilean commandos are very, very professional and they fit within the Blackwater system."

Editor's note: