Seven people have been arrested during raids at 15 addresses in Kirkby, St Helens, Knowsley village and Fazakerley.
The operation, codenamed Operation Decade, is targeting those believed to be involved in gun and drug crime.
The raids are the culmination of a 12-month investigation.
– Superintendent Paul White
Acting on information we carefully planned this initiative over 12 months and today's operation is just one example of the Force's commitment - with the support of the public and partner agencies - to tackle drug related crime and organised crime groups working in Merseyside
"These arrests send out a clear message to those involved in serious and organised crime.
"I can reassure the public that we will keep up the pressure on these organised crime groups and will pursue them relentlessly and put them before the courts to make our streets safer."
Six men and one woman, have all been arrested on suspicion of conspiracy to supply Class A drugs.
A further two men have been arrested and a substantial amount of cash has been recovered from a property in St Helens as part of the operation
The operation carried out today reinforces the Force's commitment to tackling the scourge of drugs and guns in our communities.