On October 31, 2556, Dellert was onboard the UNSC Buteo's Talon, which was docked with the Aranuka terminus high in orbit above the Pacific Ocean on Earth. At 0447 hours he sent a message to Fleet Admiral Terrence Hood as part of an ongoing conversation between the two concerning interspecies relations. In it, he let Hood know that he had learned of an operation (thanks to contacts with HIGHCOM Facility Bravo-6) wherein Fireteam Apollo was deployed to the exclusion zone around Threshold in violation of the Treaty of 2552. He also included data in the form of a translated conversation between Thel 'Vadamee and the Prophet of Stewardship, that was recovered from the black-box of Undiminished Entelechy.
On July 25, 2557, he served on the UNSC Security Council committee along with Admiral Serin Osman, Admiral Terrence Hood, General Strauss, and General Hogan. The committee was called together to debrief John-117 following the New Phoenix Incident, the destruction of Cortana and Mantle's Approach, and the defeat of the Didact. The Security Council decided to tell the general public that the incident was a Covenant attack stopped by the return of the Master Chief.
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