Page and Papadopoulos (and more recently, Michael Flynn) have shouted from the rooftops in recent months that they were entrapped and targeted by the Deep State FBI—that’s even the name of Papadopoulos’ forthcoming, fever-dream-inspired book—but the FBI started with their best interests at heart: Agents saw people with ties to the Russian government circling around the Trump campaign, and so the bureau stepped in, entirely appropriately, to monitor that activity.

The FBI was apparently alerted to this activity by its own intelligence and by tips from friendly foreign intelligence overseas. It wasn’t like these Russia-affiliated characters were necessarily new to the FBI: In 2013, agents in New York had watched as undercover officers from the Russian SVR, its foreign intelligence service, akin to the CIA, tried to recruit Page as an asset—only to determine he was too scatterbrained to be of any use.

To fully understand why these revelations matter, it helps to understand a bit about spies and the dual mission of the FBI—which is tasked not just with enforcing federal laws but also with protecting the nation from undue foreign influence.

The FBI's investigation during the 2016 presidential campaign, which we know now was codenamed Crossfire Hurricane, began as an attempt to protect Trump, to protect a political neophyte and the bizarre assortment of advisers who had surrounded him (the political equivalent of the Star Wars bar scene) from what the FBI believed were the nefarious efforts of Kremlin-linked players.

Now counterintelligence investigations, as shadowy as they are, are just that; their singular goal is to counter the specific activities of foreign intelligence services. Counterintelligence cases are markedly different from criminal cases, because when they begin the ultimate goal isn’t necessarily a pair of handcuffs and a courtroom—the goal is simply to counter the targeted actions. That can mean an arrest in some cases, but it also can mean simply watching—monitoring a suspected intelligence officer’s or agent’s routines and meetings, as the FBI evidently did with the NRA’s Russian friend, Maria Butina, for years.

It can also mean covertly disrupting or neutralizing the activity in some way, which can be as simple as showing up unannounced in US offices to warn unwitting Americans that they might have interacted with—or are about to interact with—a suspected undercover intelligence officer. (The Trump campaign did, in fact, receive so-called “defensive” briefings from the FBI to be wary that it might be the target of outreach and attempted influence from foreign powers—warnings the campaign pointedly ignored, either stupidly or conspiratorially.) At their most advanced, counterintelligence investigations can lead to the recruitment of double agents, triple agents, or the feeding of false intelligence or information back through identified spy channels.

Counterintelligence cases come with special authorities, including powerful FISA warrants for monitoring communications, along with special oversight, coordinated nationally through the Justice Department’s National Security Division—because they’re vital to the security of the United States and meant to help protect both ordinary, unwitting Americans as well as the nation’s political and military leaders.

The evolution of the FBI’s inquiry—from starting out in the spring of 2016 by attempting to protect the Trump campaign and realizing by the fall that the Trump campaign was open for business with Russia, to wondering by the spring of 2017 whether the candidate-turned-president himself was in on or even directing the plot—must have been head-spinning for the bureau and its allies in the Justice Department.

We still don’t understand nearly enough about what transpired inside the ironically paired FBI’s J. Edgar Hoover Building headquarters on one side of Pennsylvania Avenue and the Justice Department’s Robert F. Kennedy building across the street during the 10 days between FBI director James Comey’s firing and the appointment of Mueller as special counsel—the panic on the part of acting director Andrew McCabe, the befuddlement of deputy attorney general Rod Rosenstein, and the horror among agents and prosecutors. (We might know more when McCabe’s memoir comes out later this spring.)

But we know that there was evidence that deeply concerned both McCabe and Rosenstein. And we know too that we haven’t yet seen that evidence. It’s easy to forget how much of this case the FBI and Mueller know that we don’t.

For just one example: We know thanks to the bumbling of Representative Devin Nunes of California that Carter Page was targeted with a FISA warrant that was renewed three times, each for an additional 90 days, by two successive deputy attorneys general: Sally Yates and Rod Rosenstein. Each time the FISA warrant was renewed, the Justice Department would have had to demonstrate to a court that it had uncovered new intelligence showing that Page was having contact with foreign agents. What was this new intelligence? What was Page doing during this whole period, which stretched from a couple weeks before the November 2016 election right through the transition and the beginning of the Trump presidency? We don’t yet know.