A former U.S. Navy intelligence officer and FBI official from Virginia has emerged as a “key figure” in the federal investigation of the Jan. 6 Capitol breach, as U.S. prosecutors alleged Thursday that he organized a group of trained fighters and was in contact with self-styled militia groups including the Proud Boys, Oath Keepers and Three Percenters.

In asking a federal judge to detain Thomas Edward Caldwell, 66, pending trial, prosecutors revealed some of the most explicit evidence to date of discussions allegedly indicating coordination and planning among groups under scrutiny for the assault on Congress that left one police officer and four others dead, delayed the confirmation of President Biden’s victory and led to charges against more than 200 people.

Prosecutors allege Caldwell used his military and law enforcement background to plan violence — including possible snipers and weapons stashed on a boat along the Potomac River — weeks ahead of the Capitol insurrection. Caldwell, of Berryville, Va., is charged on counts of conspiracy, obstructing an official proceeding, trespassing, destruction of government property, and aiding and abetting.

Oath Keepers founder Stewart Rhodes — identified as Person One by prosecutors in documents charging Caldwell called on members of the group to “stand tall in support of President Trump” on Jan. 6. and, prosecutors say, Caldwell responded. He had been coordinating with the Oath Keepers since the week after the election, prosecutors allege, when he hosted members at his Virginia home for a pro-Trump protest that turned violent.

“Next time (and there WILL be a next time) we will have learned and we will be stronger,” he messaged others afterward, according to the court documents. “I think there will be real violence for all of us next time. . . . I am already working on the next D.C. op.”

Associates of the Oath Keepers had a chat group on the encrypted app Signal to prepare for Jan. 6, according to prosecutors, while Three Percenters met on Zoom.

Caldwell’s lawyer, Thomas K. Plofchan Jr., didn’t address the new allegations in the government brief when reached Thursday but reasserted his client’s innocence. Plofchan argued that the federal prosecutors didn’t address the two issues pending before the court — whether Caldwell, an ailing 66-year-old, is a flight risk or a danger to the community.

Many have argued that President Donald Trump's efforts amounted to an attempted coup on Jan. 6. Was it? And why does that matter? (Monica Rodman, Sarah Hashemi/The Washington Post)

Caldwell holds a top-secret security clearance and worked as both a government official and contractor, Plofchan has said. Records show Caldwell won repeated jobs for information technology work from the Drug Enforcement Administration, including one $500,000 solicitation for computer-related services.

Prosecutors alleged in Thursday’s court filing that Caldwell’s military and law enforcement background probably taught him operational tactics that he used “to the detriment of the citizens he at one time swore to serve.”

After the November protest, Caldwell suggested that in its next D.C. foray the group organize into four-man teams with snipers and getaway drivers, according to messages included in the Thursday filing. For Jan. 6., according to the court filing, he suggested stashing “heavy weapons” in a boat on the Potomac River. He shopped online for a “Surgical Steel Tomahawk Axe” and a concealed firearm built to look like a cellphone, prosecutors alleged, and discussed coordination with Proud Boys and Three Percenters.

Five people who prosecutors allege are associated with the Proud Boys were arrested Thursday and charged with crimes connected to the Jan. 6. riot. Prosecutors say several rioters appeared to be associated with the Oath Keeper and Three Percenter movements. Both are loosely organized collections of armed, right-wing groups that focus on recruiting among military and law enforcement veterans. The Proud Boys are a mostly male far-right group that has a history of violence.

On Dec. 23, Caldwell texted a contact with the Three Percenters saying that he expected Oath Keepers from North Carolina, whom he hosted in November, to return for Jan. 6, according to court documents. Prosecutors also said he expected “a big turn out of the Proud Boys” and local Vietnamese Trump supporters. One week later, prosecutors alleged, Caldwell followed up with the contact about plans by his group’s members.

The Three Percenters said on Twitter that “this guy may have reached out to a member, but nothing was coordinated. In fact, we didn’t participate in the Capitol breach.”

Caldwell also compiled a “death list” that included a state election official, prosecutors alleged, and described his political enemies as “cockroaches” and “maggots” that he would dispose of by “killing them, shooting them, and mutilating their corpses to use them as shields.”

In a statement after Caldwell’s indictment, Plofchan said Caldwell is being used as a “scapegoat” and was merely “an observer of increased frustration by some members of the public.” He did not enter the Capitol, Plofchan said, and is not an Oath Keeper.

Prosecutors say it is irrelevant whether Caldwell personally breached the building.

“Like any coach on the sideline, Caldwell was just as responsible as his players on the field for achieving what he viewed as victory that day,” they wrote.

In an interview last month, Rhodes — who has not been charged — said Caldwell “helped” Oath Keepers during the November rally because “he’s a local,” but is “not a leader of any kind.”

Among those who prosecutors allege coordinated with Caldwell before and on Jan. 6 was Jessica Watkins, a 38-year-old Oath Keeper from Ohio. She too is a “key figure” in the violence and too dangerous to be released, prosecutors said in a Thursday filing.

In a search of Watkins’s home on Jan. 17, federal authorities say they found protective equipment and battle gear, medical supplies, a mini-drone, firearms, a paintball gun, a “bomb making recipe,” zip-ties and pool cues cut down to baton size.

Both she and Caldwell, prosecutors say, “harbor . . . a doomsday mindset that, if anything, risks greater radicalization if released into a community of like-minded individuals.”

On Jan. 21, prosecutors note that Rhodes called Biden’s presidency “illegitimate” and said that while he was “not calling for the initiation of violence,” his followers should “BE PREPARED TO MOVE.”

Watkins talked about going “underground” if the attempt to keep Trump in power was unsuccessful, according to the court records. Caldwell, prosecutors say, was ready for the next fight: “So it begins,” he messaged a contact the day after the riot. “They murdered at least one of us. This is OUR Boston Massacre.”

No attorney is listed for Watkins, who told the Ohio Capital Journal in January that she didn’t commit a crime and that the riot was a peaceful protest that turned violent.

Aaron C. Davis and Tom Jackman contributed to this report.