Tobias Foucault (Earth-5875)

Commander Tobias Foucault was an officer of the UNSC Navy and captain of the prowler UNSC Red Horse, who was tasked with a reconaissance mission to the Soell system following the Battle of Installation 04 in October 2552. His ship carried a contingent of UNSC Marines led by Sergeant Zhao Heng Lopez.

Mission to the Soell system
Commander Tobias Foucault was assigned to a reconaissance mission to the Soell system following the Battle of Installation 04 in October 2552 aboard his prowler UNSC Red Horse. The initial directive was to "jump to classified coordinates, retrieve samples of an alien asset for study, conduct basic recon, expect the Covenant." Soon, he and his crew found a shuttle with a survivor that came from the prison ship Mona Lisa, to which he was given expanded orders: "Assess the status of the Mona Lisa, and if compromised beyond retrieval, destroy it."

As the mission progressed, Foucault became more than aware the Office of Naval Intelligence was not telling him everything about the situation nor the debris field of Installation 04, as well as the subsequent situation of Sergeant Zhao Heng Lopez and her Marines, who went aboard the Mona Lisa.

After he discovered about the xenomorph threat by Lopez, he became shaky and unsure on what to do. He then told Lopez that the ship would be destroyed, and that the surviving Marines had ten minutes to evacuate the ship. After the time passed, he reluctantly fired a Shiva-class nuclear missile at the Mona Lisa to contain the xenomorphs, killing Lopez, the last Marine survivor, and Henry, a sangheili prisoner.

Once Major John Smith, the responsible for the xenomorph outbreak, arrived in the Horse, Smith was detained by Foucault, who planned to have him court-martialed for his crimes against humanity.

Personality
A former robust and courageous man, Foucault became "haggard and prematurely aged" after years serving as a commander. He was cautious, taciturn, using extreme tactics when he felt they were the only options for his survival. While this led to him being declared a hero by many, he did not feel like one.