Some 150 FBI agents were involved in searches and arrests
The US has charged 22 executives or employees of security-related firms with conspiring to bribe an African country over a $15m (£9m) arms sale.
Some 150 FBI agents took part in an operation involving a sting, which led to the arrest of 21 suspects in Las Vegas and one in Miami.
Five of those charged are UK nationals and City of London Police were also involved in the operation.
The inquiry involves firms trading in arms and law enforcement equipment.
US justice officials said the charges represented the largest single investigation and prosecution carried out so far under the Foreign Corrupt Practices Act.
The law bars US citizens and companies, as well as foreign people and companies acting in the US, from bribing foreign government officials in order to get or keep business.
According to court documents, the accused engaged in a scheme to pay bribes to the minister of defence for an African country in order to win a portion of a $15m deal to outfit its presidential guard.
But the scheme was part of an undercover operation by the FBI and no minister of defence was actually involved.
As part of the sting, the accused allegedly agreed to pay a 20% "commission" to a sales agent who they believed represented the minister of defence, having been told half of that money would go to the minister.
They then allegedly agreed to create two price quotations in connection with the deal, court documents say, with one representing the true cost of the goods and the other adding the 20% "commission" to it.
The sales agent was in fact an undercover FBI agent.