Threat Assessment Index

The Threat Assessment Index (TAI) is a standardised cataloguing system used by the UNSC to rank the level of danger an organisation or group represents, such as rebel cells, colonial armed forces, and full-fledged polities. Maintained and updated by Section One of the Office of Naval Intelligence, it is intended to act as a simplified information repository for military planning, with the hope being to pre-emptively nullify competitors to the state. Although its topmost scale directly compares their ability to fight the entire UNSC, the TAI can be scaled-down to be more applicable for more localised arenas.

There are four known tiers that make up the index; grey, green, yellow, and red, in escalating order of threat. Prior to its 2553 Treaty revision, the TAI only determined the military capability these groups were determined to have. Since then, their known or suspected intent has also been factored in; because so many post-Covenant factions are able to effectively outgun the UNSC, they had to concentrate on only those that were likely to act aggressively towards them.