The Jolly Roger

The following passage in Pete Leeson's book on pirates reminded me of my earlier post about why rapists shouldn't be treated as harshly as rapists who are also murders (emphasis added):

The presence of these other belligerent marine vessels provides a clue why pirates went through the trouble of using the Jolly Roger when they attacked their prey: Pirates wanted to distinguish themselves from the other assaulting vessels merchant ships might encounter. Britain criticized the Spanish Guarda Costa for inhumanely treating some British prisoners it captured. Nevertheless, at least in principle, the viciousness coast guard vessels could show toward merchant crews they assaulted was limited because they were government-sanctioned cruisers. They weren't permitted to wantonly slaughter merchant crews that resisted them after these crews cried out for quarter, for instance. In contrast, pirates weren't even theoretically constrained in how they treated those they overcame. Pirates were outlaws and would be hanged if authorities captured them whether they massacred merchant crews they attacked or not. In this sense, for pirates, massacring resistors was essentially costless.

Thus, the skull-and-crossbones Jolly Roger served as a credible signal to merchant ships that they should surrender instead of face probable death.