A coalition of dozens of law enforcement agencies arrested more than 1,000 pimps and sex buyers in a summer-long series of prostitution stings.

The months-long annual sting, now known as the National Johns Suppression Initiative, was led by Sheriff Tom Dart of Cook County, Il. A total of 39 law enforcement agencies across 18 states arrested 961 men trying to buy sex and 71 pimps or traffickers, more than in any of his previous stings.

About two-fifths of the arrests stemmed from online prostitution ads, and 98% of those ads were placed on Backpage.com, according to a press release from the sheriff’s office. In the four years since the annual sting began, more than 4,000 sex buyers and traffickers have been arrested (it used to be called the National Day of Johns).

“This broad national movement should send a strong message to prospective johns that sex trafficking simply is not a victimless crime,” said Sheriff Dart in a statement. “These women and girls have been brutalized and exploited – and the most effective way to deter these heinous crimes is to target the demand.”

Read more Catching Johns: Inside the National Push to Arrest Men Who Buy Sex

The Cook County Sheriff’s office has repeatedly attacked Backpage.com as a haven for pimps and traffickers, and earlier this summer asked Visa and Mastercard to withdraw their credit cards as a form of payment on the site. Backpage.com won a temporary restraining order against Sheriff Dart in July, but in August a judge denied an injunction request that would have forced Dart to retract his statements about the website, concluding that Dart’s requests to Visa and Mastercard did not count as censorship. Backpage.com did not immediately reply to requests for comment.

Occasionally, officers encountered children while carrying out the stings. The Cook County Sheriff’s Office arrested a man who was attempting to buy sex with his 2-year old daughter in the car, and the St Paul, Mn. police department arrested a trafficker who was holding his victim’s 3-year old son in order to keep her from going to the police. Dayton, Oh. police recovered a 15-year old runaway who they said was being prostituted on Backpage.com.

Read more about the national push to target men who buy sex here.

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Write to Charlotte Alter at charlotte.alter@time.com.