A few weeks ago, a person inside Mosul began to send text messages to Iraqi military intelligence in Baghdad.

Abu Bakr al-Baghdadi, the leader of Islamic State, “has become intemperate,” said the early November message, written by an informant inside the city who has contact with the group but is not a member of it.

“He has cut down on his movements and neglects his appearance,” the message read. “He lives underground and has tunnels that stretch to different areas. He doesn’t sleep without his suicide bomber vest so he can set it off if he’s captured.”

The text message, which Reuters has seen, was one of many describing what was happening inside Islamic State as Iraqi, Kurdish and American troops began their campaign to retake the group’s northern Iraqi stronghold of Mosul.

The texts, along with interviews with senior Kurdish officials and recently captured Islamic State fighters, offer an unusually detailed picture of the extremist group and its leader’s state of mind as they make what may be their last stand in Iraq. The messages describe a group and its leader that remain lethal, but that are also seized by growing suspicion and paranoia.

Defectors or informants were being regularly executed, the person texted. Baghdadi, who declared himself the caliph of a huge swathe of Iraq and Syria two years ago, had become especially suspicious of people close to him. “Sometimes he used to joke around,” one text said. “But now he no longer does.”

While Reuters has verified the identity of the informant who has been texting Iraqi military intelligence, the news agency couldn’t independently confirm the information in the messages. But the picture that emerges fits with intelligence cited by two Kurdish officials – Masrour Barzani, head of the Kurdistan Regional Government’s (KRG) Security Council, and Lahur Talabany, who is chief of counter-terrorism and director of the KRG intelligence agency.

Talabany and other intelligence chiefs said the military coalition is making slow but steady progress against Islamic State. The coalition has formidable assets inside Mosul, they said, including trained informers and residents who provide more basic surveillance by texting or phoning from the city’s outskirts. Some of the informants have families in Kurdistan whom the KRG pays.

The Kurds believe that the military assault on Mosul, which began on October 17, is fueling Islamic State’s sense of fear and mistrust. In the short term, they said, the group’s obsession with rooting out anyone who might betray it may help rally fighters to defend Mosul. But the obsession also means the group has turned inwards right as it faces the most serious threat to its existence in Iraq since seizing around a third of the country’s territory in the summer of 2014.

The number of executions is a clear sign Islamic State is beginning to hurt, said Karim Sinjari, interior minister and acting defense minister with the KRG, which controls the Kurdish area in northern Iraq.

As well, he said, many of the group’s local Iraqi fighters lack the “strong belief in martyrdom that the jihadis have.”

“Most of the die-hard Islamists who are fighting to the death are foreign fighters, but their numbers at the frontline are less than before because they are getting killed in battle and in suicide attacks,” he said.

Barzani said the growing paranoia has pushed Baghdadi and his top lieutenants to move around a lot, further hurting the group’s ability to defend the city. Baghdadi, Barzani said, “is using all the different tactics to hide and protect himself: changing positions, using different ways of traveling, living in different locations, using different communications.”

If the military coalition does push Islamic State from Mosul, the Kurdish officials said, the group is likely to flee to Syria, from where it will pose a nagging threat to Iraq through regular suicide attacks and other guerilla tactics.