Destruction of Yavin 4

Soon after the escape of Grand Alliance operatives off of Yavin 4], Supreme Leader [[Victor Nevarez ordered Lord Commander Reginar Albrecht to destroy the natural satellite base.

Prelude

 * "That wretched French boy has disrupted my plans, but his foolish act will not go unpunished. Come to me on Exegol, Commander Albrecht"
 * "As I served you for years now, I'm still loyal to you, Supreme Leader."
 * "Send the Deathshead to a world they know. Let it burn. The Immortal Armada rises, he will come, his friends will follow."
 * "It will be done, my lord."
 * --Victor Nevarez and Reginar Albrecht

Shortly after the duel on Kef Bir, a crew of Resistance members, except for Jedi apprentice Rey, returned to the Ajan Kloss base in defeat. Soon after, they learned of Leia Organa's death.

Victor later contacted Reginar via hologram and ordered him to send the Deathshead; a Xyston II-class Star Destroyer, to a world the Alliance was familiar with.

Destruction

 * "Captain, Yavin 4 is in range."
 * "Fire."

--Milon Lenwith and Chesille Sabrond

The Xyston II-class Star Destroyer Deathshead was sent to Yavin 4, and, after Captain Chesille Sabrond gave the command, its upgraded superlaser destroyed the entire moon.

Aftermath

 * "The Supreme Leader sent the Deathshead from the Moon? Does that mean that every ship in that armada..."
 * "...has planet-killing antimatter weapons. Of course they do. All of them. This is how he finishes it."
 * --Beaumont Kin and Poe Dameron

The Alliance soon learned about the world's destruction. Due to Organa's death, Poe Dameron was made general. Going to her corpse, Dameron admitted to her that he did not know what to do and said he was not ready. Just then Galactic Civil War veteran General Lando Calrissian arrived, informing Dameron that he, Organa, Han Solo, and Luke Skywalker had also not been ready for their war. After Dameron asked how they were able to defeat the Galactic Empire with almost nothing, Calrissian responded that they had each other.

Learning from this, Dameron made Finn a general, and Finn revealed the droid D-O had some information on Exegol. After learning that Alexander Pepper sent intel to R2-D2 regarding the map to Exegol, the Resistance developed a plan to attack the Immortal Armada while Calrissian and Chewbacca would use the Millennium Falcon to call out for allies.