Re: What happened to the Valiant....
What we do know from the Episode "A Taste of Armageddon":
- Anan 7 used a device that made his voice sound 98% like Kirk's. He could have done the same trick with the remaining crew aboard USS Valiant to lure them down to the planet and their deaths. But in this case, what happened to the ship? It seemed Anan 7 was conceding not to destroy the Enterprise: "If possible, we shall spare your ship, Captain, but its passengers and crew are already dead."
- Scotty had only raised the deflector shields because Kirk and company had been long overdue: "Screens firm, sir. Extremely powerful sonic vibrations. Decibels eighteen to the twelfth power. If those screens weren't up, we'd be totally disrupted by now." The USS Valiant may not have raised its shields in time and became disrupted. Or Anan 7's predecessor opened fire upon the Valiant the moment it was declared a casualty of war.
"The first duty of every Starfleet officer is to the truth" Jean-Luc Picard
"We can't solve problems by using the same kind of thinking we used when we created them." Albert Einstein