Treason within?

https://www.snopes.com/fact-check/cicero-treason-quote/

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Although these words are now widely attributed to Cicero, in fact they originated in the 20th century, with novelist Taylor Caldwell’s 1965 book A Pillar of Iron. Even though that work often drew directly from the recorded speeches and letters of Cicero for its dialogue, it was nonetheless a work of fiction, and the warning from Cicero about “treason from within” was an invention of Caldwell’s and not a reproduction of Cicero’s own words.