Drugs with an estimated street value of £5m have been seized by police in raids in Wirral and Greater Manchester.
Police raided seven properties in New Brighton, Wallasey, Bidston and Heswall, and searched another address in Greater Manchester on Friday.
They uncovered more than 650kg of cannabis, 16.5kg of heroin, a firearm and a substantial amount of ammunition.
Four people have been charged with drugs offences and are due to appear before Wirral magistrates later.
Four others arrested in the raids were interviewed and have been released on bail pending further inquiries.
Merseyside Police arrested the eight people on suspicion of possession of a controlled drug with intent to supply.
Officers from the Matrix team seized 16.5kg of what is believed to be heroin from a house in Wallasey.
Between 150 and 200kg of cannabis was uncovered at a property in Bidston, along with the firearm and ammunition.
About 500kg of cannabis was later found at a house in Greater Manchester, with an estimated street value of £3.5m.