From Halopedia, the Halo wiki
This article is about the gametype. For the Halo: Reach armor permutation, see Armor accessories/Assault.
Assault is a multiplayer gametype in Halo 2, Halo 3, Halo: Reach, Halo 2: Anniversary and Halo 5: Guardians where one team attempts to 'arm' a bomb in the opponents base. This 'arming' requires the player carrying the bomb to occupy a designated circle in the enemies base for a predetermined amount of time. This is a task greatly aided by Sticky Arming. The bomb will be visible to all players when it is not being carried except in single bomb and multi-bomb games when a team has not removed the bomb from its original spawn site. However, once an opponent has picked up the bomb, it disappears and can only be viewed when seen by you or a teammate. Also after the it has been dropped. It is easy to be seen however, due to its bright glow.
Halo 2: Anniversary
Halo 5: Guardians
The human Assault bomb has messages written on it.