Fail-Safe Detonation is a term that is used to explain the self-destruct system of a WIA or KIA SPARTAN-II's armor. Once a SPARTAN-II is killed or wounded fatally, the protocol will have to be enacted by either themselves or a nearby Spartan. This is done to avoid capture of the suit and/or the wearer for identification or technological study. It is unknown if the Mark VI has this capability, since the Mark V is said to have one.[1]


The tiny access panel at the back of the suit is opened to activate the protocol, it is activated by typing several digits only Spartans know. Once activated, a fifteen-second countdown timer starts. Once it hits zero, the suit's fusion reactor overloads and burns everything in its path in a ten-meter radius with a follow-up explosion to finish anything alive.[2]


  • John-117 is the only known Spartan to activate the fail-safe detonation (on Grace-093's suit after she was killed by a Jiralhanae in the Covenant city of Unyielding Hierophant).[3]
  • It is known that activation of the armor's fusion reactor is part of the Cole Protocol and failure to activate the core when possible will result in court martial and/or stripping of rank.


  1. Halo: First Strike, page 315
  2. Halo: First Strike, page 315
  3. Halo: First Strike, page 315