Twenty men have been arrested as part of a large investigation into human trafficking, drug dealing and money laundering across England.
Thames Valley Police said more than 300 officers raided 18 properties in Reading on Wednesday, following the eight-month probe into organised crime.
Seven addresses were also raided across Blackburn, Sunderland, Birmingham and London.
Officers said a "significant amount" of cash, drugs and weapons were seized.
Thames Valley Police, which carried out the raids with the National Crime Agency and the South East Regional Organised Crime Unit, said the 20 suspects, aged between 19 and 38, had been arrested on suspicion of various offences, including drug offences.
Det Insp Natalie Hall said it had been a "complex and time-consuming" investigation.
"I hope that this serves as a warning to those in the community who are involved in the supply and distribution of drugs as well as the exploitation of people, that we know who you are, where you are and we are committed to bringing you to justice," she added.