The object was twofold. One was to destroy an opponent's logistics base and discourage supporters. The other was to bait the opponent into leaving a good defensive position and coming out into the open, where he could be attacked; a noble needed strong nerves and a stony heart to stay behind walls while his subjects were slaughtered and his lands destroyed.

Medieval English kings were not nice people. Edward III (1312–1377), in particular, used his son the Black Prince to wage a form of warfare called chevauchée, which consisted of killing and burning everyone and everything that could be reached by fast-moving raiders.

As many have noted during the past week, Robert Mueller and his legal sell-swords must have been aware for nigh onto two years, at least, that the accusation that Trump's campaign colluded with the Russians had no evidentiary support. Nonetheless, per the attorney general's summary letter to Congress, the investigation spent tens of millions of dollars, employed 19 lawyers and 40 other professional staff, issued 2,800 subpoenas, executed 500 search warrants, obtained more than 230 orders for communications records, authorized almost 50 pen registers, made 13 document requests to foreign governments, and interviewed 500 witnesses.

Barr and Mueller seem to regard this recounting as cause for satisfaction, as evidence of great diligence by the Department of Justice. But each of these actions inflicted substantial expense and career damage on those unlucky enough to be caught up in it. Every one of those witnesses should have lawyered up, knowing the ruthlessness of prosecutors on the scent of a big-time case. The game is to find something on a lower-level person and threaten him with heavy penalties unless he gives the prosecutor a more tempting target. If no extortionary material can be found, the witness can be accused of lying to the FBI, with the proof consisting of notes taken by the interviewing FBI agents themselves, since the agency refuses to make recordings. Family members can be threatened.

Most of these witnesses have kept quiet about the experience, content to have escaped. Some are speaking out, such as Michael Caputo, who has written eloquently and repeatedly about the costs imposed on him and others.

Sundance, at Conservative Treehouse, concludes that none of this investigating was really directed at the collusion charge. It was all an effort to entrap Trump himself or at least some of his supporters into actions that could be branded as "obstruction of justice," with that term broadly interpreted to encompass almost any action he took.

When Trump said Michael Flynn was a "good guy," this was spun as "obstruction." When he wanted to release FISA memos, he was warned that this would be "obstruction." Any reaching out to witnesses would have been branded "obstruction." Any statement of sympathy for Paul Manafort or Roger Stone would have been obstruction gold.

In this view, which is persuasive, the collateral damage inflicted on those on the fringes of the investigation was not in fact collateral — it was the point. Mueller was running a chevauchée designed to inflict pain and, in Sundance's words, "to goad President Trump into something Mueller could then color/construe as obstruction and then open House impeachment [proceedings]." Sundance thinks Mueller's staff may have been ready to escalate by indicting Trump family members (for nothing to do with Russia) and were stopped only by new A.G. William Barr's calling a halt.

Logically, the chevauchée should have worked. Given Trump's aggressive nature and tendency to wield Twitter like an axe, one would have expected him to come out from behind his walls of lawyers and engage, and it is to the credit of those lawyers that they prevented this. Had Mueller's team gone after his family...

Unfortunately, the tactic worked in other ways. Competent people will hesitate before coming to work for this or any other conservative administration, knowing they can be financially ruined at the whim of political potentates or prosecutors and that they must navigate a world in which the well connected can violate laws at a whim while the disfavored are accused of lying to the FBI if they assert their innocence.

At a recent speech, Trump said repeatedly that this must never happen to another president, but the president is only a part of it. If we want competent government, his servants must be protected as well.

Specific suggestions for reform are harder to come by. Three possibilities come to mind:

First, it not time to let bygones be bygones. After the 2016 election, Trump seemed willing to do this, but instead of reciprocity, he got a vicious attack. If he fails to get to the bottom of the Steele dossier, the FISA warrants, and the other perversions, he will receive contempt rather than gratitude or truce, and future Deep State operatives will draw the lesson that they can pervert the system without fear of accountability.

Second, somebody, perhaps in the DOJ, needs to examine the collateral damage from this probe and set compensation for it, including compensation for someone such as Flynn, who has gone broke while pleading guilty to a nonsensical process crime. (Flynn is accused of lying to the FBI about his conversation with the Russian ambassador when Flynn knew that the FBI had a recording of it. At a trial, it should take a jury five minutes to find a lack of both intent and materiality, but Flynn is broke, and Mueller may have threatened his son.)

Third, on reading accounts of the Black Prince, one wonders, "Where were England's religious leaders? Were they okay with chevauchée?" Now one would like to put the same question to the high priests of the U.S. legal system, such as the chief justice and the deans of the major law schools: "are you okay with this perverse use of the legal system, in which the process is both a severe punishment and a way of entrapping people who are not guilty of other crimes?" Answers may not be easy, but one would like to see the legal grandees at least take ownership of the problem.

Long ago, in a universe far away, James V DeLong was book review editor of the Harvard Law Review.