In the end it was a bridge that gave away the militants.

An investigative journalist says he or she has identified the location used by members of the Islamic State to train a new batch of recruits, all based off clues left in a series of photographs.

See also: How the Islamic State Lures Child Recruits to Fight in Syria and Iraq

The photos, which show about 80 men, dressed head to toe in combat gear in some kind of training camp, were posted by a terrorist-affiliated media Twitter account in July. On Friday, the citizen journalist, who wrote at Bellingcat — a collaborative website founded by the blogger Eliot Higgins earlier this year — published a post that concluded the IS recruits were operating on a stretch of road along the Tigris River in Mosul, Iraq.

An undated photograph posted by a pro-ISIS Twitter account a class of recruits posing after completing a training program with the Islamic State. Image: Bellingcat/Militant website

"Have you ever wondered what it would be like to go through training as an ISIS terrorist? Or better yet, where you would go to find such advanced training?" the contributor, who wrote it under an anonymous byline, asked in the post.

"All you have to do to find the answer to these questions is turn to the nearest ISIS media twitter account and click on that bright blue Justpaste.it link," the writer says, referring to the website of choice for militants looking to share photos of their latest exploits.

The journalist did that by using a variety of online tools — Google Earth, FlashEarth and Panoramio — to pinpoint landmarks in the photographs that could be used to identify the location where militants practiced martial arts, marched with guns or posed for the end-of-camp group picture seen above.

There was a bridge that spanned the Tigris River. There was a series of billboards on the side of a road. And there was an unmistakable tower.

By triangulating those locations on a map, the journalist determined it was on the stretch of road in the image below where the fighters learned their murderous tradecraft sometime earlier this summer.

A map Image: Google Earth/Bellingcat

Iraqi and Kurdish forces recaptured Iraq's largest dam from Islamic militants Monday following dozens of U.S. airstrikes, President Barack Obama said, in the first major defeat for the extremists since they swept across the country this summer.

Militants from the Islamic State group had seized a dam near Mosul on Aug. 7, giving them access and control of enormous power and water reserves and threatening to deny those resources to much of Iraq.

Iraqi forces suffered a string of humiliating defeats at the hands of the Islamic State as the extremists took over large parts of northern and western Iraq and sent religious minorities fleeing.

The militants' battlefield victories brought U.S. forces back into the conflict for the first time since it withdrew its troops in 2011 and reflected the growing international concern about the Sunni extremist group. Washington launched attacks from its warplanes and drones on Aug. 8.

Since then, U.S. Central Command says it has conducted a total of 93 airstrikes across Iraq. Of that total, 60 airstrikes were conducted in support of Iraqi forces near Mosul's Dam, CENTCOM said on Friday.

The Associated Press contributed to this report.