In this occasional series, we will bring you up to speed on the biggest national security stories of the week.

1. Can President Trump fire Attorney General Jeff Sessions? What are the consequences?

Yes. Cabinet officials serve at the pleasure of the president and can be fired for any cause or no cause. However, the politics and legality of firing this particular official at this particular time would be fraught, because special counsel Robert S. Mueller III is already investigating Trump’s intentions around his repeated attempts to force or shame Sessions into quitting, to determine whether those efforts are part of a broader pattern of attempted obstruction of justice. Firing Sessions, a former senator from Alabama, could provoke a fierce response in Congress, where many Republicans are still very supportive of their former colleague and where many Democrats fear that the president is willing to tear apart the Justice Department to torpedo the Russia probe.

2. If Trump fires Sessions, who would step in? What would happen to the Russia investigation?

It depends on how he does it. If he appointed a temporary replacement, that person could, in theory, take over supervision of the Russian probe from Deputy Attorney General Rod J. Rosenstein. Rosenstein has been overseeing the Russia probe because Sessions recused himself from investigative matters related to the 2016 campaign. Alternately, if Sessions were fired, Rosenstein could assume the title of acting attorney general, in which case the same person would be overseeing the Russia probe, but that person would also be the top official at the Justice Department.

3. Has Sessions ever fired back against Trump?

Sessions has generally laid low when the president publicly criticizes him. On Wednesday, after the president attacked the attorney general in a tweet pushing for a more aggressive investigation of alleged surveillance abuses against a former Trump campaign aide, Sessions took the rare step of issuing a statement, saying that as long as he was the attorney general, he would continue to do the job “with integrity and honor.” The statement suggests that Sessions felt Wednesday’s attack was more alarming than previous complaints from the president.

4. How unusual is it for the president to criticize the attorney general so publicly?

It is very unusual. Presidents have been known to grouse privately about their attorney general or FBI director. What Trump has done, though, is regularly air his dislike of his attorney general, which current and former Justice Department officials have called a worrisome sign for the long-term credibility and stability of the department. Part of the reason Trump’s critics are so alarmed by his comments about Sessions is that he appears to want Sessions to use the department’s investigative powers to fight the president’s political battles.

5. Will Sessions continue to take the criticism? 

The attorney general’s statement Wednesday seemed to be a reassertion that he has no plans to resign and is willing to endure public ridicule from the commander in chief to stay in the job. Trump’s broadsides have had an odd political effect — while many Democrats disagree with Sessions and distrust his stewardship of the department, they also fear that if Sessions were forced out, what follows could be more partisan and tumultuous.