After a tumultuous week in which he ordered American troops to leave Syria, his Secretary of Defense James Mattis resigned in protest, and he shut down the government after failing to reach a deal on border wall funding, President Trump canceled his plans to travel to Florida and instead stayed behind in the White House—where he apparently decided to get into the holiday spirit by settling scores on Twitter.

The Twitter firestorm began Sunday with Trump again pleading his case for the border wall. “The only way to stop drugs, gangs, human trafficking, criminal elements and much else from coming into our Country is with a Wall or Barrier,” Trump wrote, in an apparent attempt to justify his decision to shut down the government until he gets the $5 billion in border wall funding he demanded. “Drones and all of the rest are wonderful and lots of fun, but it is only a good old fashioned Wall that works!”

It continued with the bombshell announcement that Mattis, who was originally expected to stay on as Defense Secretary through February to ensure a stable transition, would be leaving next week, a move reportedly prompted by Trump’s irritation with all the positive news coverage Mattis received for the thinly veiled rebuke of Trump he included in his resignation letter.

Trump appeared to hit back hard on Sunday with the surprise news that Mattis’ replacement, the Pentagon's second in command Patrick Shanahan, would be taking over as acting Defense Secretary on Jan. 1. The president praised Shanahan as “very talented” and with a “long list of accomplishments,” just hours after taking a swipe at Mattis.

“When President Obama ingloriously fired Jim Mattis, I gave him a second chance. Some thought I shouldn’t, I thought I should,” he tweeted late Saturday.

Trump then doubled down on his decision to withdraw from Syria, a move that has been decried by lawmakers (and cable news hosts) on both sides of the aisle as a gift to ISIS and other U.S. foes.

“We signed two pieces of major legislation this week, Criminal Justice Reform and the Farm Bill. These are two Big Deals,” Trump said. “But all the Fake News Media wants to talk about is ‘the mistake’ of bringing our young people back home from the Never Ending Wars. It all began 19 years ago!”

Next in his sights was Sen. Bob Corker (R-TN), a vocal Trump critic who bashed the president Sunday while speaking on CNN’s State of the Union. Corker told host Jake Tapper that Trump knows he “made a mistake” in choosing to withdraw from Syria, and called the demand for a border wall a “made up fight.”

Trump responded with a pair of furious tweets attacking Corker not for his statements, but for his upcoming retirement. “Senator Bob Corker just stated that, ‘I’m so priveledged ( sic ) to serve in the Senate for twelve years, and that’s what I told the people of our state that’s what I’d do, serve for two terms.’ But that is Not True - wanted to run but poll numbers TANKED when I wouldn’t endorse him,” Trump claimed, adding that “Bob Corker was responsible for giving us the horrible Iran Nuclear Deal, which I ended, yet he badmouths me for wanting to bring our young people safely back home. Bob wanted to run and asked for my endorsement. I said NO and the game was over. #MAGA I LOVE TENNESSEE!”

Sen. Corker responded with a biting rebuke of that claim. “Yes,” he wrote, “just like Mexico is paying for the wall... #AlertTheDaycareStaff.”