Large scale Operations conducted by the UNSC against the Covenant and their colonies. Due to being on the defensive, the UNSC adopted a literal ring of defenses. Mostly made up of ODP's, these planets had upwards of 100 Sabre Hangars and between 300-4000 Orbital Defence Platforms. The UNSC fleets stationed at each planet would be significant too. Whilst the command and control vessel of the picket fleet could be any light ship class (Frigates), they provide the first wall of rocks to break the wave of fighters and strike bombers from reaching the Orbital Defence Ring and are usually situated by the Slip Lanes.
@sloosecannon Thanks for fixing my from before, I'll delete the original post and do it properly this time. Thanks again, though. :)