Colonel Phillip Green was a despotic militia leader on Earth in the 21st century during World War III. Green, known for his motto: "Overwhelm and devastate", was notorious for striking at his enemies during treaty negotiations. (TOS: "The Savage Curtain")
Barely two years after a cease-fire had ended the war, he ordered the euthanasia of hundreds of thousands of radiation sickened Humans so they would not pass on mutations to future generations. Green outlined his rationale by speaking to a crowd about how they must "reject the impure and cast it out".
This act was met with mixed feelings by survivors, many regarding him as nothing more than a genocidal madman. Others would see him as a pragmatic visionary who "humanely" euthanized radiation-afflicted individuals, preventing those afflicted and their descendants from passing on deadly mutations and the suffering that would come with that. (ENT: "Demons")
This controversial and contentious posthumous view of Green resulted in heated debates about him and the impact of his policies for many years; among the students of Green's teachings years afterward, John Frederick Paxton made use of his ideologies to lead a group known as Terra Prime in an unsuccessful bid to expel all non-humans from the Sol system in 2155. (ENT: "Terra Prime")
"Overwhelm and devastate."
"We must reject the impure and cast it out."
"This is not a time for timidity and second guessing. We cannot afford to doubt ourselves."
"To be human is to be pure."
"I have no quarrel with you, any more than you have with me!" (Excalbian duplicate)
"Men don't talk peace unless they're ready to back it up with war." (Excalbian duplicate)
"History tends to exaggerate." (Excalbian duplicate)
Green was played by actor Phillip Pine in "The Savage Curtain", and by Steven Rankin in "Demons". Green's first name was given as "Phillip" in a barely-legible graphic seen in "In a Mirror, Darkly, Part II". The name was likely chosen in reference to the first name of the character's original actor. The tone in which he addressed Surak as, "...Vulcan!" in the former episode may have been some insight into his xenophobic attitude towards aliens.
In early drafts of the Augments trilogy in the fourth season of Star Trek: Enterprise, Manny Coto had intended to use Green as the villain of the piece, played by Peter Weller. After he learned that Brent Spiner was interested in a role on the series, Coto re-wrote his script to accommodate Spiner and created the character of Arik Soong.  Green's appearance on Enterprise would have featured the logo of the Fourth World military (as shown in "Encounter at Farpoint"), here used as Green's personal command emblem. After Green was removed from the Augments arc, the only other appearance of that emblem was in "In a Mirror, Darkly". Weller would eventually appear at the end of the fourth season as John Frederick Paxton, Green's greatest admirer, in "Demons" and "Terra Prime".