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Mission to Soell
In October 2552, he was assigned to a top-secret recon mission in Installation 04's debris field in the Soell system. The initial mission objectives were to "jump to coordinates classified higher than top secret, retrieve samples of an alien artifact for study, conduct basic recon, expect Covenant trouble." As soon as the crew found a lifepod with a survivor from the prison ship Mona Lisa, Foucault was shown the expanded orders: "Assess the status of the Mona Lisa, and if compromised beyond retrieval, destroy."
Throughout the mission, he was aware that he did not know everything that was going on with the situation around the Installation 04 debris field, and later, the situation of the squad aboard the Mona Lisa and why the Red Horse was brought there. He knew the recently transferred "smart" AI Rebecca knew more, but was unwilling to share as per her orders.
As the mission progressed and it was evident that his squad on the Mona Lisa could be in harm's way, he was reluctant to follow Rebecca's suggestions to make their orders priority as he tried to find out what was happening and help his squad. In the face of unknowns, with the in-the-know AI making some strong suggestions, he was determined to not abandon his men and fire at the Flood-infested Mona Lisa.
After Rebecca finally revealed the Flood threat, Foucault became shaky in his resolve, unsure about what actions he should take. He finally told Lopez (who was on the Mona Lisa) that the ship had to be destroyed, and the crew on the Mona Lisa had eight to ten minutes to evacuate. Following protocol, Foucault reluctantly fired a Shiva-class nuclear missile at the Mona Lisa, with Sergeant Lopez still on board as the last human survivor.
As Major John Smith, the ONI operative responsible for the Flood outbreak on the Mona Lisa, boarded the Red Horse, having stolen the Marines' Pelican and in doing so attracted the attention of the Covenant capital ship in the system, Foucault ordered the Major to be detained, later planning to have him court-martialed.
Personality and traits
Before his promotion to the rank of commander, Foucault was a robust man. By the time of the mission aboard the Mona Lisa, however, he seemed "haggard and thin and prematurely aging." Commander Foucault was a cautious man who used extreme tactics when it had seemed the only option for his continued survival. It had made him a hero and given him his command, but he did not feel like a hero. At times Foucault dislikes his command, wishing he were a private and in a firefight rather than making overarching high-level and distant decisions.
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