Stephen K. Bannon has always been more comfortable when he was trying to tear down institutions — not work inside them.

With his return to Breitbart News, Mr. Bannon will be free to lead the kind of ferocious assault on the political establishment that he relishes, even if sometimes that means turning his wrath on the White House itself.

Hours after his ouster from the West Wing, he was named to his former position of executive chairman at the hard-charging right-wing website and led its evening editorial meeting. And Mr. Bannon appeared eager to move onto his next fight.

“In many ways, I think I can be more effective fighting from the outside for the agenda President Trump ran on,” he said Friday. “And anyone who stands in our way, we will go to war with.”