The man known as Abu Ubaydah Al Lubnani (“the Lebanese”) is one of the most senior al Qaeda leaders to defect to the Islamic State since the two jihadist organizations split in early 2014. Lubnani was once a top security official for al Qaeda in Afghanistan and Pakistan. But after being demoted from his sensitive post, he joined Abu Bakr al Baghdadi’s organization. Lubnani quickly became a thorn in al Qaeda’s side, revealing details about his former employer’s inner workings.

Earlier this year, Lubnani’s story was featured in several editions of the Islamic State’s Al Naba newsletter. The contents of his testimony are so explosive that an al Qaeda operative known as Abu Karima al Khorasani was forced to respond.

One issue, more than any other, loomed large in their debate: Al Qaeda’s relationship with Iran.

In the 19th edition of Al Naba, an interviewer asked Lubnani how he managed to travel from the Khorasan (an area that encompasses Afghanistan and Pakistan) to the caliphate’s home in Syria after his falling out with al Qaeda’s leadership.