Phineas and Ferb replace Catherine Halsey in the halo timeline.

Catherine Halsey was never born in all rounds. With the backing and resources of the entirety of the UNSC. do they win the human-covenant war?

R1: As above. They have the full backing of the UNSC.

R2: Phineas and Ferb have access to their normal resources, and are rogue agents.

R3: They have the full backing of the UNSC, but Thaddius and Thor have the full support of the covenant and their vastly more advanced technology.