After marrying Prince Harry -- who's a trained combat vet himself -- Meghan will undergo military training from the British Special Air Service on how to deal with a hostage situation -- S.O.P. for Royal newbies.

Meghan's hostage training will last about a week, and it will teach her techniques on how to transmit a distress signal that she's being held against her will if her captors make her record a video ... this according to Scott Jones, director of the London-based security firm Garvian.

Meghan's training will include mastering micro-expressions, key words and other signals to let either her family or law enforcement know if she's under duress from captors. We're also told she'll get some basic psychology training on dealing with her captors.

She'll also be taught how to get out of restraints ... like duct tape or zip ties.

Another source who served in the British Armed Forces tells us Meghan's hostage training will be primarily geared toward facilitating a rescue, and would probably not include combat or weapons training.

BTW ... Meghan is following in the footsteps of her princess predecessors like Diana and Kate. Both of them underwent similar training after joining the Royal Family. They both did it at a Special Air Service base in Hereford ... so it'd make sense for Meghan to go there as well.

Good luck.