In the Discover Hope trailer shown at last
year's E3, "Brohammer' tells Master Chief
that they lost as he looks at the Halo ring.
Clearly, some battle occurred at Zeta Halo
between the UNSC and some enemy force.
At the time, it seemed obvious that it was a
battle between Created and UNSC forces.
However, we now know of the Banished.
Since we know that the Banished will be in
Halo Infinite (and likely at Zeta Halo), it may
have been them that beat the UNSC there.
And what about whoever found the Pelican
at the end of the trailer? Might that be the
Banished? Or could it be something else?