Changing of the Guard
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After the assassination of the High Prophet of Regret by John-117, the remaining two Hierarchs made the unilateral decision to reassign the Sangheili Honor Guards, replacing them instead with Jiralhanae. While the Hierarchs claimed that the Sangheili were no longer capable of protecting them, in reality, the Prophet of Truth had abandoned Regret to his fate, in order to solidify his control over the Covenant.
The Changing of the Guard sparked outrage amongst the Elites, who viewed it as an insult to their people. The High Prophet of Truth took a dismissive approach to the early rumblings of discontent, deeming the event merely an "exchange of hats". However, not only had the Hierarchs made the decision without consulting the High Council, but the order itself was in flagrant violation of the Writ of Union, the founding document of the Covenant. Subsequently, the Elites on the Council threatened to resign. In response, the High Prophets declared the Sangheili to be traitors to the Covenant, and encouraged the other races to turn against their former commanders and remain loyal to the Prophets, igniting the civil war.
However, the High Prophets had not foreseen the support the Sangheili still had among much of the Covenant. Many Unggoy and Mgalekgolo continued to follow their Sangheili masters and joined the Arbiter's Fleet of Retribution, and the conflict between them and the now Jiralhanae-led Covenant troops loyal to the Prophets began the Great Schism.
"Changing of the Guard" is a phrase used in modern-day Britain, as well as Commonwealth countries, signifying the changing between different shifts of guards who protect the royal family and government.
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