The highest ranking corps of the papal military service.
It originated in the Cavelleggieri (light cavalry) which formed the mounted guard of the popes.
Reorganized several times, it assumed its present name under Pope Pius VII, 1815, new regulations being given by Pope Leo XIII.
The pope appoints the commander, always a Roman prince, and all members must show a 60 years line of nobility recognized in the Papal States.
Their only public appearance is with the pope at public functions, withdrawing when he does; the privilege of conveying the tidings to newly appointed cardinals belongs exclusively to them.
New Catholic Dictionary