Steve Bannon flipped Sen. Jeff Flake's announcement Tuesday that he would not seek re-election into a warning to all remaining "establishment Republicans" he aims to unseat in 2018.

"Our movement will defeat you in primaries or force you to retire," Bannon said, according to Breitbart News Network Editor-in-Chief Alex Marlow. "The days of establishment Republicans who oppose the people's America First agenda are numbered," he added, referring to a principle championed by President Trump.

Bannon left the White House in August and almost immediately returned to Breitbart News as executive chairman.

Breitbart News also celebrated the news from Flake, R-Ariz., tweeting "WINNING" multiple times.

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WINN https://t.co/XOT6IO0K3r — Breitbart News (@BreitbartNews) October 24, 2017

In recent months, Bannon has declared a "season of war" against establishment Republicans in the Senate who are up for re-election. Bannon plans to support primary challengers facing off against every Republican incumbent in 2018, except for Sen. Ted Cruz, R-Texas.

Last week, Bannon appeared at a campaign event for Kelli Ward in Arizona, who had been challenging Flake for the GOP nomination.

Flake, who has been a vocal detractor of Trump's, panned the president Tuesday while announcing his intention not to run in 2018.