WASHINGTON - The U.S. defense secretary and the top military officer told members of Congress on Thursday that they still do not know who gave the order to clear protesters near the White House ahead of President Donald Trump's walk to St. John's Church last month.

"It's still unclear to me," Defense Secretary Mark Esper told the House Armed Services Committee when asked who gave the order to clear the protesters in Lafayette Square, adding that he had not pursued the topic.

"I find that hard to believe," Committee Chairman Adam Smith replied.

Chairman of the Joint Chiefs of Staff General Mark Milley also said he did not have "personal knowledge" on who gave the order for law enforcement to clear the square on June 1.

Active duty troops were never used to aid law enforcement amid protests following the death of African American George Floyd while he was in police custody. Esper and Milley reiterated Thursday that the National Guard troops who were there served as a "backup" to law enforcement and did not engage in clearing protesters.

"The Guard did not advance on the ground. The Guard did not shoot rubber bullets. The Guard did not employ chemical agents of any type. Rather, the Guard remained in a static role," Esper said.

Former leaders critical

The  forceful dispersing of protesters at Lafayette Square ahead of Trump's walk to St. John's Church last month drew criticism from former military leaders, including retired General Jim Mattis, the former secretary of defense, and retired Admiral Mike Mullen, a former chairman of the Joint Chiefs of Staff.

While military troops were not seen engaging with protesters, military helicopters were filmed flying low in Washington in what appeared to be an intimidation tactic to clear protesters from the area.

Esper said Thursday that an Army investigation into possible misuse of National Guard helicopters was completed and should be available for lawmakers to view next week.

In light of the recent widespread U.S. protests against the death of Floyd, Milley acknowledged Thursday that both the United States and its military are struggling with racism and have "much more to do" on the path to equality.

"Divisiveness leads to defeat," he said, later warning the committee that foreign adversaries are trying to take advantage of current civil unrest in the U.S.

Review of symbols

The head of the Joint Chiefs of Staff also called for a "hard look" at Confederate symbols on U.S. military installations in order to make sure the military is a place where all Americans see themselves represented.

"There is no place in our armed forces for manifestations or symbols of racism, bias or discrimination," Milley said.

"Some think it's heritage. Others think it's hate," he added when asked about the Confederate flag.

The Marines and U.S. Forces Korea have already banned displaying the Confederate flag on their military grounds, and the Navy is in the process of drafting a ban as well.

When asked about a potential militarywide ban, Esper on Thursday deferred to the review process that had been directed.

"There is a process underway by which we affirm what types of flags are authorized on U.S. military bases. I want to make sure we have an approach that is enduring, that can withstand legal challenge, but that unites us," he said.

Trump has defended the display of Confederate symbols, speaking out against NASCAR for banning the Confederate battle flag and chastising Army leadership on Twitter for considering renaming 10 bases that are currently named for Confederate leaders.