(NewsNation) — Ahead of President Joe Biden’s address announcing the death of Osama bin Laden’s successor, Al-Qaeda leader Ayman al-Zawahiri, NewsNation host Leland Vittert — who interviewed his brother, Muhammad al-Zawahiri — joined “Rush Hour” to provide context on the significance and purpose of the hit.

According the Vittert, the “big take away” here is that, while Osama bin Laden has largely remained a fixture and figurehead of Islamic terrorism worldwide, Ayman al-Zawahiri, has remained a legitimaite theat.

“Ayman al-Zawahiri was the world’s No. 1 terrorist,” Vittert said. “He was one of the original terrorists; he was part of the assasination of Anwar Sādāt in Egypt.”

And it was the death of Egypt’s former president, Vittert said, that led to what we now think of as modern Islamic terrorism, which includes everything from the attacks on the U.S. embassies to the Twin Towers bombings in ’93 to the World Trade Center attacks of 9/11.

“al-Zawahiri’s video on September 10th of 2012 is what inspired (the) Bengahzi attacks and the killing of four Americans. The blood of countless American shouldiers who were in Iraq — perticularly in Afgahnistan — are on his hands,” Vittert said.

All this is why the counterrorsm mission, which was reportedly successful in killing him, is a big deal, Vittert says — regardless of how long ago the terrorism he inspired took place.

“Every minute that these terrorists spend worried about their operational security and their physical security — worried about the United States coming after them — is one less minute they have to plan and plot attacks,” he said.

Check out the rest of the interview above.