The Reuters news agency said on Thursday that the ambitious intelligence operation began in February, when Turkish authorities captured a close aide to Abu Bakr al-Baghdadi, the Iraqi-born leader of the group known as Islamic State of Iraq and Syria (ISIS). According to Hisham al-Hashimi, security advisor to the government of Iraq, the ISIS aide was Ismail al-Eithawi, also known by his alias, Abu Zaid al-Iraqi. Iraqi officials claim that al-Eithawi was appointed by al-Baghdadi to handle the secret transfer of ISIS funds to bank accounts around the world.

It appears that al-Eithawi had managed to escape to Turkey when the United States-led coalition shattered ISIS’ self-proclaimed caliphate. But he was captured by Turkish counterterrorism forces and handed over to Iraqi authorities. Baghdad then shared the contents of al-Eithawi’s cell phone with US intelligence officers. The latter were able to help their Iraqi counterparts utilize the popular messaging app WhatsApp, a version of which was installed on al-Eithawi’s cell phone. According to al-Hashimi, the Iraqis and Americans made it seem like al-Eithawi was calling an emergency face-to-face meeting between senior ISIS commanders in the area. But when these Syria-based commanders crossed into Iraq to meet in secret, they were captured by Iraqi and American forces.

According to al-Hashimi, those captured include a Syrian and two Iraqi ISIS field commanders. More importantly, they include Saddam Jamal, a notorious ISIS fighter who rose through the ranks to become the organization’s governor of the Euphrates’ region, located on Syria’s east. Al-Hashimi told reporters on Thursday that Jamal and al-Eithawi were the most senior ISIS figures to have ever been captured alive by US-led coalition forces. The Iraqi government advisor also said that al-Eithawi’s captors were able to uncover a treasure trove of covert bank accounts belonging to ISIS, as well as several pages of secret communication codes used by the militant group.