Fifteen people have been arrested on suspicion of drugs trafficking after Class As worth an estimated £5m were seized in a series of raids.
About 30 warrants were executed in Merseyside, Greater Manchester, South Wales, Devon and Cornwall.
It follows a major investigation into the trafficking of drugs into the south west and South Wales between March 2017 and November 2018.
Heroin, cocaine and amphetamine with an estimated value of £5m were seized.
It is alleged that members of organised crime groups in Merseyside relocated to Devon to arrange the supply of drugs in a so-called county lines operation.
The term refers to the practice of criminal gangs exploiting vulnerable people and using them to transport, deal or store drugs.
Eight men, aged between 19 and 53, were arrested at a number of locations in the south west, including Plymouth, Exeter and Cullompton.
A further four people were arrested in Merseyside and three in South Wales.
Det Insp Ben Davies from Devon and Cornwall Police said: "This type of crime preys on some of the most vulnerable in our society, who are then coerced and exploited as part of the drug trade".