Five Bradford men have been arrested on suspicion of illegally bringing guns into Britain from the US.
The men, aged between 23 and 32, were arrested by firearms officers on Thursday night and are in custody.
The operation involved West Yorkshire Police, the Serious Organised Crime Agency and the USA's Bureau of Alcohol, Tobacco, Firearms and Explosives.
Police said the presence of guns in Yorkshire communities would not be tolerated.
The arrests followed raids at addresses in Bradford, Leeds and Pontefract.