On the evening in question, Nixon ordered AG Richardson to fire Archibald Cox, the Special Prosecutor investigating the Watergate break-in. Instead, Richardson resigned, making deputy AG William Ruckleshaus acting AG (momentarily). Nixon repeated the order, and Ruckleshaus also resigned, which put the Solicitor General, Robert Bork, in the hot seat.
Bork wrote the letter of dismissal, per orders.
But what if he hadn’t? How many officials did Nixon have on hand that night? I’m picturing a string of guys lined up outside the Oval Office, like the passengers from that scene in Airplane!, all waiting their turn to “calm down” the hysterical lady.
From a brief Google foray under “line of succession for attorney general” it sounds like pretty much the entire Justice Dept. would step up starting with the most senior US Attorney. It’s not clear, though, what would happen if they went through all the US Attorneys.
My understanding was that Richardson, Ruckelshaus, and Bork were all at the Justice Department all day. Richardson went over to the White House (and resigned) and then returned to Justice. Ruckelshaus was then called on the phone, and resigned.
Bork then spoke with Haig on the phone and was summoned to the White House as acting AG.
Presumably they could have kept calling people into the office, but I think that the three of them had decided that Bork would not resign (at least in part to avoid having to answer the question you’ve posed).
But the “action” was at Justice, not at the Oval Office. I also think they they decided that Bork would comply with the order before Richardson went to the White House, but I may not recall that correctly.