It was the little things that led American hunters to the most dangerous prey of all — 9/11 mastermind Osama bin Laden, according to a new book.

Bin Laden, 54, was killed by U.S. special forces on May 2, 2011, after being the leader of the Sept. 11, 2001, terrorist attacks on the United States.

Peter Bergen, a national security analyst for CNN, said in “The Rise and Fall of Osama bin Laden” that the little things included how the members in bin Laden’s compound hung out the laundry to dry, according to excerpts printed in the New York Post.

Bergen notes in the book — due out Tuesday and published by Simon & Schuster — that bin Laden believed that in order to be a true Muslim, all of his wives should live with him in one massive multi-generational family. That turned out to be a major clue.

As the initial hunt for bin Laden appeared to be bogged down, Bergen wrote, bin Laden bodyguard Ibrahim Saeed Ahmed abd al-Hamid was tasked with getting a compound ready for bin Laden, who began moving into the Abbottabad, Pakistan, home in 2005.

In 2010, those hunting bin Laden caught a break: Al-Hamid was spotted in Peshawar.

In August of that year, Central Intelligence Agency agents trailed the bodyguard to the compound, which was surrounded by 18-foot-high, barbed-wire-topped walls, according to the book, per the Post.

At that point, bin Laden lived there with his three wives, eight of his children and four grandchildren.

And the clotheslines helped give the situation away.

Day after day, clothes for men, women and children — including babies — flapped in the breeze. The clothes did not mesh with the 11 members of the bodyguards’ families.

The final clue was the clotheslines on the compound, which flapped each day with women’s garments#OsamaBinLaden #Spies #Article #Military https://t.co/jT79u65GID

— H24 News US (@h24news_us) July 31, 2021

The laundry seemed to indicate that the kind of family they were seeking was inside.

But that wasn’t all. Other pieces of the puzzle added to something more than an ordinary family living there. There was no land line or internet. Also, windows were very few, and a balcony was surrounded by a high wall.

“Who puts a privacy wall around a patio?” then-CIA Director Leon Panetta asked, according to the book, via the Post.

“Exactly,” one analyst replied in the book.

The house also was noteworthy because people there burned all of their garbage.

On Dec. 14, 2010, Panetta made the case to then-President Barack Obama that they had found bin Laden.

They never had pictures to prove he lived there, but “they also never found evidence that undercut the notion that he was living there,” Bergen wrote.

The planning began, resulting in the 2011 raid that killed bin Laden.