Sen. Deb Fischer, a Nebraska Republican, questioned Hegseth about investing in the United States nuclear arsenal and whether he agreed with Trump's posture during his first administration -- that preventing attacks from adversaries was the "highest priority."

"Yes, I do, because ultimately, our deterrence, our survival is reliant upon the capability, the perception and the reality of the capability of our nuclear triad," Hegseth responded. "We have to invest in its modernization for the defense of our nation."

Committee chairman Sen. Roger Wicker, R-Miss., in the first question of the hearing, asked Hegseth to respond to the allegations against him.

"Let's get into this allegation about sexual assault, inappropriate workplace behavior, alcohol abuse and financial mismanagement during your time as a nonprofit executive," Wicker said.

Hegseth, who has denied the accusations, railed against what he claimed was a "coordinated smear campaign" by the news media.

"All they were out to do, Mr. Chairman, was to destroy me," Hegseth said. "And why do they want to destroy me? Because I'm a change agent and a threat to them. Because Donald Trump was willing to choose me, to empower me to bring the Defense Department back to what it really should be, which is war fighting."

Hegseth then turned personal, saying he's not "perfect" but is now ready to lead the Pentagon.

"I'm not a perfect person, but redemption is real," he said. "And God forged me in ways that I know I'm prepared for."

Hegseth is now speaking for the first time before the committee.

His opening statement is being interrupted by hecklers, who were then escorted out of the room.

Chairman Roger Wicker thanked authorities for their "swift reaction" to the first incident.

"Let me just say this, the Capitol Police are going to remove immediately individuals who are interrupting the hearing," Wicker said.

Trump's pick for national security adviser, Rep. Mike Waltz, introduced and endorsed Hegseth.

Waltz was recognized by Sen. Roger Wicker, the chairman of the committee, who noted Waltz was still a member of Congress for several more days.

"He will bring the perspective of being the first secretary of defense to have served as a junior officer on the front lines, not in the headquarters on the front lines in the War on Terror, and recognizes the human costs, the financial costs and the policy drift that was discussed often in this very room that led us to decades and decades of war," Waltz said of Hegseth.

Waltz is also a retired Army National Guard officer and war veteran.