ONI Directive 930

ONI Directive 930 is a UNSC regulation pertaining to publicity of the SPARTAN-II supersoldiers. It created a tradition which eventually extended to the SPARTAN-IIIs as well.

When the UNSC went public with the SPARTAN-II program, the Office of Naval Intelligence, Section Two, issued a directive to falsify the circumstances surrounding the deaths of any Spartans. This was because they feared that reports of Spartan losses would cause a crippling loss of morale. This protocol maintains the illusion that Spartans can't die.

The Protocol
Office of Naval Intelligence Section Two Directive 930

To maintain morale among the forces of the UNSC, any Spartan casualties are to be listed as MISSING IN ACTION or WOUNDED IN ACTION.

SPARTAN-III
Just before his death, Lieutenant Commander Kurt Ambrose lists the status of two deceased SPARTAN-III's as MIA, "adhering to the tradition of never listing a fallen Spartan as 'killed in action' ". However, this was likely more sentimental than official, as the MIA directive was specific to the SPARTAN-IIs publicity, whereas the SPARTAN-III Program was designed never to go public.