NEW YORK (CBSNewYork) — Former New York Mayor Rudy Giuliani had quite the gaffe while speaking before Donald Trump’s foreign policy speech in Ohio on Monday.

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Giuliani, who was the mayor during the 9/11 terror attacks, said that there were no successful terrorist attacks in the United States in the eight years before President Barack Obama came into office.

Rudy Giuliani on Pence, 9/11 and no successful radical Islamic terrorist attacks in the U.S. before President Obama.https://t.co/mCT15iRsq9 — CSPAN (@cspan) August 15, 2016

“By the way, under those eight years before Obama came along, we didn’t have any successful radical Islamic terrorist attacks in the United States. They all started when Clinton and Obama got into office,” Giuliani said.

Obama took the oath of office in 2009.

However, right before the gaffe, Giuliani was talking about the Sept. 11 terror attacks.

“Remember, we didn’t start this war, they did. We don’t want this war, they do. And they didn’t start it even in 2001, they attacked the World Trade Center in 1993 and they attacked it under the ideology of radical Islamic extremism to create a caliphate, to destroy the infidels – Christians, Jews, non-believing Muslims from their point of view and other people,” the former mayor said.

Giuliani even described Republican vice presidential nominee Mike Pence visiting Ground Zero while he was a member of Congress.

“Mike Pence understands this, from his time both on the Foreign Affairs Committee, from his very, very timely visit which I remember to Ground Zero when we were in desperate need of help, he was there, and from his work on the Judiciary Committee in helping to fashion the Patriot Act,” he said.

Twitter to Giuliani to task for the slight.

here's a photo of a memorial in the middle of manhattan that according to giuliani apparently exists for no reason pic.twitter.com/Uncb1jvwEx — Oliver Willis (@owillis) August 15, 2016

2008 giuliani: we must never forget 9/11

2016 giuliani: nine what — Johnny GD Roosevelt (@footstepsfaIco) August 15, 2016

Giuliani, not thinking about 9/11 for the first time in 15 years https://t.co/lU4KfqgWNf — Luke O'Neil (@lukeoneil47) August 15, 2016

For a time millions of us admired Giuliani for his handling of 9/11 on that horrible day. How far he has fallen! https://t.co/ub6NmwTdPB — (((sfpelosi))) (@sfpelosi) August 15, 2016

Has anyone in American political history ever squandered more good will than Rudy Giuliani? — Ken Tremendous (@KenTremendous) August 15, 2016

https://t.co/kYNUqrQyhy RT @jessicaschulb: Giuliani: Before Obama, we didnt have any successful radical Islamic terrorist attacks inside US" — Chris Herring (@HerringWSJ) August 15, 2016

Hmm… Rudy Giuliani is trending. Let's see what he says…. *checks* pic.twitter.com/iXaBwuvQBf — Matt Maybray (@MattMaybray) August 15, 2016

I don't know why everyone's mad at Rudy Giuliani. The terrorists attacked on 9/11 because they knew Obama would be the next president. — Cassandra Nicholson (@WriterWarrior) August 15, 2016

Rudy Giuliani was born the same year as me. Hate to see such remarkable memory loss in someone my age. — Oh_opa (@opabinia_seabug) August 15, 2016

Giuliani forgetting about 9/11 is like your mom calling to ask when your birthday is. — LOLGOP (@LOLGOP) August 15, 2016

More than 3,000 people died in the Sept. 11 terror attacks.