FBI agents kept away from the Malheur National Wildlife Refuge for weeks based on what they knew about occupation leader Ammon Bundy and his armed supporters and Bundy's pledge to take a "hard stand" and turn the property into a base for patriots for years, according to testimony Tuesday from the man who led the police response.

"For us to go in there, we believe would provoke a confrontation," said Greg Bretzing, who just retired as Oregon's FBI special agent in charge.

His top three goals, he said, were to end the takeover peacefully, return the refuge to the control of the U.S Fish & Wildlife Service and hold those involved in the armed occupation accountable.

"To quote-unquote 'assault the refuge' would have compromised the primary goal,'' Bretzing said.

The government called Bretzing as its first witness as the second trial of Oregon standoff defendants began.

Prosecutors were trying to get out in front of questions that dogged them during the first trial last fall when jurors acquitted Bundy and six others: Why did the FBI allow the occupiers to travel freely to and from the refuge? Why didn't police and FBI agents move in right away when the occupiers seized the refuge on Jan. 2, 2016? How did the FBI use confidential informants in its investigation?

Yet on cross-examination, defense lawyers forcefully questioned Bretzing about whether the FBI properly followed its guidelines in using the informants and if Bretzing was aware that at least one informant may have "aided and abetted" occupiers and engaged in unlawful conduct by providing training on guns and hand-to-hand combat.

Andrew Kohlmetz, defendant Jason Patrick's standby lawyer, pointed out that Bretzing didn't want to expose his agents to potential harm but had no problem sending confidential informants - civilians -- into the refuge during the occupation.

Kohlmetz asked Bretzing if he personally approved any of the informants engaging in criminal activity on the refuge?

"I don't recall specifically approving," Bretzing replied.

Kohlmetz asked if any other FBI special agents in charge from other divisions around the country gave their approval.

"I'm not aware of that, no,'' Bretzing said.

Kohlmetz asked Bretzing if he was aware that an informant named Fabio Minoggio provided firearms training to occupiers.

"Specifically, I'm not aware of that,'' Bretzing said.

Or hand-to-hand combat training? "No, I'm not aware of that,'' Bretzing replied.

Bretzing said he learned of the refuge seizure by a text message or email on the day it happened and then arrived in Burns two days later. He was aware of the roles Ammon Bundy, Ryan Bundy and Ryan Payne played in the 2014 armed standoff with federal land management officers outside the ranch of the Bundys' father, Cliven Bundy, near Bunkerville, Nevada.

The FBI presence grew from two agents in Burns on Jan. 2, 2016, the date of a rally and march in support of Harney County ranchers Dwight Hammond Jr. and Steven Hammond, to 25 to 50 law enforcement officers working out of a command center set up in a former junior high school in Burns within days.

It was decided that Harney County Sheriff Dave Ward would serve as the intermediary with Ammon Bundy because of the animus Bundy and supporters had toward the federal government, Bretzing said.

"We hoped for greater success by engaging them through the sheriff and local law enforcement," Bretzing testified.

He and Ward held joint morning briefings for officers during the course of the occupation and Bretzing said he attended several community meetings in Burns to help gauge the community's reaction to the takeover.

Bretzing confirmed that the FBI used drones, fixed cameras and overhead planes to do surveillance over the 41-day occupation. During cross-examination, he said there might have been FBI surveillance cameras and license readers placed in Burns. The U.S. military was never involved, he said, and informants were indeed sent into the refuge.

"We had several people willing to go out to the refuge and tell us what was happening," he testified. "I sent in people who could inconspicuously observe what was going on.''

Asked why he didn't arrest Ammon Bundy or other leaders sooner when they traveled into Burns or home to their families, Bretzing said that would have left a group of other leaders back at the refuge to rally in their support and continue the occupation.

Instead, the FBI learned a day or two before a scheduled Jan. 26 community meeting in John Day that Ammon Bundy and a group of the occupation leaders planned to go. The agents learned who would be traveling there, in what vehicles and their route, Bretzing said. He confirmed that the man who drove Ammon Bundy to John Day that day, Mark McConnell, was an FBI informant.

The decision was made to arrest "the core group of leaders" in a remote spot as they traveled along U.S. 395 to John Day. Bretzing called the arrests a "valid law enforcement action to bring this to a close."

He acknowledged that occupation spokesman Robert "LaVoy" Finicum was fatally shot by state troopers during the Jan. 26, 2016 police stop, but didn't say a word about a continuing federal investigation into alleged misconduct by FBI hostage rescue team agents at the scene.

Defense lawyer Michele Kohler, who represents Duane Ehmer, suggested that some area sheriffs expressed dissatisfaction with the FBI's wait-and-see approach.

"There is no doubt that during the several weeks there was very robust discussion on how best to bring this to a close," Bretzing responded.

Kohler also asked if some FBI agents called to Burns or the refuge were told to remove their badges to conceal their identities as federal law officers. Bretzing said there were times when agents manning the gates to the command center would wear vests that said "police" because of anger against the federal government.

During cross-examination, Bretzing acknowledged that he authorized FBI agents to contact local militia groups, such as the Pacific Patriot Network.

Bretzing, saying repeatedly that he didn't know specifics about certain informants such as Minoggio, noted that he delegated certain responsibilities to other supervisory agents.

But he added, "Anything that happened at the end of the day will always come back to the special agent in charge."

Bretzing is expected to return to the stand Wednesday morning for further cross-examination.

He retired about three weeks ago and now works as director of local security for The Greenbriar Companies.