Halo 5's 4-Player Co-Op Allows for a Much More Sociable Story - GameSpot

Microsoft explains why it's focusing so heavily on four-player co-op with the upcoming game.
A new entry in the Halo franchise was announced at the Microsoft Press Conference at E3 2013 for the Xbox One.

Cooperative play - Halopedia, the Halo wiki

Halo 5: Guardians Review - GameSpot

Halo 5: Guardians review: An old friend - CNET

Halo Infinite Campaign Network Co-Op Flight Preview : r/Games

Actually, Halo 5's Campaign Co-Op Does Require Xbox Live Gold - GameSpot

343 Admits They Screwed Up With Halo 5's Story

Halo 5: Guardians – Xbox One : Microsoft Corporation

Resistance 2 - Wikipedia

Halo 5's story sees Master Chief team up with Blue Team in single-player and co-op

Halo Infinite's King Of The Hill Twist On Firefight Co-Op Arrives On December 5 - GameSpot

Halo 5: Guardians features exciting 4-player co-op and new enemies

Halo 5: Guardians – Xbox One : Microsoft Corporation

Halo 5: Guardians Review - GameSpot