A Black Operation (or Black Op) is a covert operation by a government, a government agency, or a military organization. This can include activities by private companies or groups. Key features of a black operation are that it is secret and it is not attributable to the organization carrying it out. The main difference between a black operation and one that is merely secret is that a black operation involves a significant degree of deception, to conceal who is behind it or to make it appear that some other entity is responsible.
A "black bag operation"; is primarily used for covert or clandestine surreptitious entries into structures to obtain information for human intelligence operations. Such operations are known to have been carried out by the FBI, the CIA, Mossad, MI6, ISI (Pakistan), RAW, MSS, and the intelligence services of other nations.
Season 3[]
Navy SEALs Lieutenant Commander Steve McGarrett and Lieutenant Commander Freddie Hart were assigned on a deep Black Op mission to North Korea. So secretive, that if they died their Government would deny any involvement, and their families would never know what happened. They both had to HALO jump to get into the country undetected. This was to be expected for men of their station, both Navy SEALs and having trained under Commander Joe White.
Their mission was to collect Anton Hesse at the time being under the protection of militia who worked for Han Ji-Woon but the mission ended in tragedy when Hart suffered fatal injuries and later died with Steve being forced to abandon him in North Korea.