Washington (CNN) ISIS is facing cash and manpower shortages, the deputy commander of the counter-ISIS coalition said Tuesday.

His statement was reinforced by newly obtained internal ISIS documents. The cache shows the group struggling for funds -- some of which are used to pay for sex slaves -- and calling on fighters to use less electricity and stop driving official cars for personal use. The fighters, meanwhile, seem to be suffering low morale, in some case seeking doctors' notes to avoid serving on the frontlines.

Iraqi government forces patrol in southern Falluja, Iraq, on June 10, 2016. In late June, a senior Iraqi general announced that the battle to reclaim Falluja from ISIS had been won.

A boy walks past bloodstains and debris at a cafe in Balad, Iraq, that was attacked by ISIS gunmen on May 13, 2016. Twenty people were killed.

A boy walks past bloodstains and debris at a cafe in Balad, Iraq, that was attacked by ISIS gunmen on May 13, 2016. Twenty people were killed.

Two wounded women sit in the airport in Brussels, Belgium, after two explosions rocked the facility on March 22, 2016. A subway station in the city was also targeted in terrorist attacks that killed at least 30 people and injured hundreds more. Investigators say the suspects belonged to the same ISIS network that was behind the Paris terror attacks in November.

Members of Iraq's elite counterterrorism unit celebrate December 28, 2015, after recapturing the city of Ramadi. The city fell to ISIS in May 2015.

Law enforcement officers search a residential area in San Bernardino, California, after a mass shooting killed at least 14 people and injured 21 on December 2, 2015. The shooters -- Syed Rizwan Farook and his wife, Tashfeen Malik -- were fatally shot in a gunbattle with police hours after the initial incident. The couple supported ISIS and had been planning the attack for some time, investigators said.

Spectators at the Stade de France in Paris run onto the soccer field after explosions were heard outside the stadium on November 13, 2015. Three teams of gun-wielding ISIS militants hit six locations around the city, killing at least 129 people and wounding hundreds.

Two women hold hands after an explosion in Suruc, Turkey, on July 20, 2015. The blast occurred at the Amara Cultural Park, where a group was calling for help to rebuild the Syrian city of Kobani, CNN Turk reported. At least 32 people were killed and at least 100 were wounded in the bombing. Turkish authorities said they believed ISIS was involved in the explosion.

A man inspects the aftermath of a car bombing in Khan Bani Saad, Iraq, on July 18, 2015. A suicide bomber with an ice truck, promising cheap relief from the scorching summer heat, lured more than 100 people to their deaths. ISIS claimed responsibility on Twitter.

ISIS also claimed responsibility for what it called a suicide bombing at the Al-Sadiq mosque in Kuwait City on June 26, 2015. At least 27 people were killed and at least 227 were wounded, state media reported at the time. The bombing came on the same day as the attack on the Tunisian beach.

Dead bodies lie near a beachside hotel in Sousse, Tunisia, after a gunman opened fire on June 26, 2015. ISIS claimed responsibility for the attack, which killed at least 38 people and wounded at least 36 others, many of them Western tourists. Two U.S. officials said they believed the attack might have been inspired by ISIS but not directed by it.

In May 2015, ISIS took control of Palmyra, Syria, and began to destroy ancient ruins and artifacts. The Temple of Bel is seen here after Syrian forces reclaimed the city in March 2016. ISIS has also destroyed other cultural sites in Syria and Iraq.

An Iraqi soldier searches for ISIS fighters in Tikrit on March 30, 2015. Iraqi forces retook the city after it had been in ISIS control since June 2014.

In March 2015, ISIS released video and images of a man being thrown off a rooftop in Raqqa, Syria. In the last photograph, the man is seen face down, surrounded by a small crowd of men carrying weapons and rocks. The caption reads "stoned to death." The victim was brutally killed because he was accused of being gay.

In February 2015, British newspapers report the identity of "Jihadi John," the disguised man with a British accent who had appeared in ISIS videos executing Western hostages. The militant was identified as Mohammed Emwazi, a Kuwaiti-born Londoner. On November 12, 2015, the Pentagon announced that Emwazi was in a vehicle hit by a drone strike. ISIS later confirmed his death.

Safi al-Kasasbeh, right, receives condolences from tribal leaders at his home village near Karak, Jordan, on February 4, 2015. Al-Kasasbeh's son, Jordanian pilot Moath al-Kasasbeh, was burned alive in a video that was released by ISIS militants. Jordan is one of a handful of Middle Eastern nations taking part in the U.S.-led military coalition against ISIS.

A Kurdish marksman stands atop a building as he looks at the destroyed Syrian town of Kobani on January 30, 2015. After four months of fighting, Peshmerga forces liberated the city from the grip of ISIS.

ISIS militants stand near the site of an airstrike near the Turkey-Syria border on October 23, 2014. The United States and several Arab nations began bombing ISIS targets in Syria to take out the group's ability to command, train and resupply its fighters.

On August 19, 2014, American journalist James Foley was decapitated by ISIS militants in a video posted on YouTube. A month later, they released videos showing the executions of American journalist Steven Sotloff and British aid worker David Haines.

Aziza Hamid, a 15-year-old Iraqi girl, cries for her father while she and other Yazidi people are flown to safety after a dramatic rescue operation at Iraq's Mount Sinjar on August 11, 2014. A CNN crew was on the flight, which took diapers, milk, water and food to the site where as many as 70,000 people were trapped by ISIS. Only a few of them were able to fly back on the helicopter with the Iraqi Air Force and Kurdish Peshmerga fighters.

ISIS fighters parade down an Iraqi street in this image released by the group in July 2014.

ISIS fighters parade down an Iraqi street in this image released by the group in July 2014.

Traffic from Mosul lines up at a checkpoint in Kalak, Iraq, on June 14, 2014. Thousands of people fled Mosul after it was overrun by ISIS.

Kurdish Peshmerga fighters fire missiles during clashes with ISIS in Jalawla, Iraq, on June 14, 2014. That month, ISIS took control of Mosul and Tikrit, two major cities in northern Iraq.

Kurdish Peshmerga fighters fire missiles during clashes with ISIS in Jalawla, Iraq, on June 14, 2014. That month, ISIS took control of Mosul and Tikrit, two major cities in northern Iraq.

The ISIS militant group -- led by Abu Bakr al-Baghdadi, pictured -- began as a splinter group of al Qaeda. Its aim is to create an Islamic state, or caliphate, across Iraq and Syria. It is implementing Sharia law, rooted in eighth-century Islam, to establish a society that mirrors the region's ancient past. It is known for killing dozens of people at a time and carrying out public executions.

People flee the scene of a terror attack at Istanbul's Ataturk airport on June 29. Turkish officials have strong evidence that ISIS leadership was involved in the planning of the attack, a senior government source told CNN. Officials believe the men -- identified by state media as being from Russia, Uzbekistan and Kyrgyzstan -- entered Turkey from the ISIS stronghold of Raqqa in Syria, bringing with them the suicide vests and bombs used in the attack, the source said.

Maj. Gen. Peter E. Gersten told reporters that attacks on ISIS finances and personnel had reduced the number of foreign fighters joining ISIS from 1,500-2,000 per month a year ago to 200 per month today.

"We're actually seeing an increase in now the desertion rates in these fighters. We're seeing a fracture in their morale. We're seeing their inability to pay. We're watching them try to leave Daesh," Gersten said, using another name for ISIS.

Since October, the U.S.-led anti-ISIS coalition has been targeting the group's oil infrastructure and cash storage facilities in an effort to undermine ISIS' finances. Gersten said that the strikes had destroyed between $300 million to $800 million and promised additional strikes on ISIS finances.

Photos: Syrian forces retake Palmyra Photos: Syrian forces retake Palmyra Syrian military engineers detonate mines laid by ISIS militants during an operation to liberate the city of Palmyra, Syria, on Sunday, March 27. Syrian forces recaptured Palmyra from ISIS on Sunday, months after the city fell to the Islamic extremist group, state media reported. Hide Caption 1 of 18 Photos: Syrian forces retake Palmyra A member of the Syrian military walks past a banner bearing ISIS slogans on March 27. Hide Caption 2 of 18 Photos: Syrian forces retake Palmyra Smoke rises near a gas station as a result of fighting between Syrian government forces and ISIS militants on March 27. Hide Caption 3 of 18 Photos: Syrian forces retake Palmyra Damage to the Palmyra Castle, the ancient hilltop citadel formally known as Fakhr-al-Din al-Maani Castle, can be seen following the fighting on March 27. Hide Caption 4 of 18 Photos: Syrian forces retake Palmyra Syrian soldiers carry a wounded comrade after an explosion near the castle on Saturday, March 26. Hide Caption 5 of 18 Photos: Syrian forces retake Palmyra Syrian soldiers climb to the top of the castle to place a flag on March 26. Hide Caption 6 of 18 Photos: Syrian forces retake Palmyra Syrian forces hold a position on the outskirts of Palmyra on March 26. Hide Caption 7 of 18 Photos: Syrian forces retake Palmyra Syrian forces pose next to the Palmyra Castle on March 26. Hide Caption 8 of 18 Photos: Syrian forces retake Palmyra Syrian soldiers stand near the body of an ISIS militant near Palmyra on Friday, March 25. Hide Caption 9 of 18 Photos: Syrian forces retake Palmyra A dust cloud rises near the Palmyra Castle during the military operation to retake Palmyra on March 25. Hide Caption 10 of 18 Photos: Syrian forces retake Palmyra Syrian soldiers survey the damage to a villa belonging to the Qatari royal family on March 25. The villa near Palmyra served as an ISIS headquarters after being abandoned by its owner. Hide Caption 11 of 18 Photos: Syrian forces retake Palmyra Syrian troops hold a position on the outskirts of Palmyra on March 25. Hide Caption 12 of 18 Photos: Syrian forces retake Palmyra Syrian soldiers fire mortars at ISIS positions in Palmyra on March 25. Hide Caption 13 of 18 Photos: Syrian forces retake Palmyra Syrian soldiers reload a cannon near Palmyra on Thursday, March 24. Hide Caption 14 of 18 Photos: Syrian forces retake Palmyra A Syrian soldier takes a position inside a damaged palace at the entrance of Palmyra on March 24. Hide Caption 15 of 18 Photos: Syrian forces retake Palmyra Syrian troops monitor the surrounding area from their location on the outskirts of Palmyra on March 24. Hide Caption 16 of 18 Photos: Syrian forces retake Palmyra Smoke rises near Palmyra during the operation to retake the town on March 24. Hide Caption 17 of 18 Photos: Syrian forces retake Palmyra Syrian troops stand next to a mansion belonging to the Qatari royal family on March 24. Hide Caption 18 of 18

"If it's one dollar bill on the street that they're using to build a weapon, I'm going to go after that one dollar," he said.

Aymenn al-Tamimi, the Jihad-Intel Research Fellow at the Washington-based Middle East Forum think tank, who obtained the ISIS documents, wrote in a paper accompanying their release Friday that, "The internal records make clear these pressures have been felt in the group's military, financial, and administrative domains."

Al-Tamimi acquired the documents from activists, journalists and former residents of the area controlled by the Islamic State. Some of the documents were recovered from areas recently liberated by local U.S. allies from ISIS control.

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The memos were first published in the CTC Sentinel, a product of the Combating Terrorism Center at West Point overseen by CNN terrorism analyst Paul Cruickshank.

"While it was not feasible for Aymenn al-Tamimi to verify the documents with ISIS administrators in Syria, careful examination by al-Tamimi of their content, format and appearance found them to be consistent with documents drafted by ISIS in the past and generated no red flags," Cruickshank said.

The official ISIS records give an up-to-date look at the terrorist organization, with some of them dated as recently as March 2016.

Photos: Blueprints of war: Syrian artists paint the struggle Photos: Blueprints of war: Syrian artists paint the struggle The posters by Fares Cachoux are simple and haunting. Though he was living abroad as the civil war broke out in his homeland, he wanted to show the world the stories coming out of Syria. His most recent poster reflects on what the International Organization for Migration says were nearly 1 million refugees who have attempted to cross the Mediterranean in 2015 for safer land. Half of these people are Syrian. "The sea graveyard for countless Syrians attempting to cross to escape DEATH. ... She awaits in the depths of the waves of the Mediterranean," the caption reads in French below the work he sent to CNN. Hide Caption 1 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Cartoonist Hossam Alsaadi ran a coffee shop used as a haven by young Syrians who opposed their nation's regime at the start of the civil war. Now, those coffee shops are few and far between. The United Nations estimates more than 400,000 people in dozens of villages are under siege, many of them having to live off salt, water and grass to survive. Aid deliveries have become rare for those who cannot join the 11 million people who have had to abandon their homes. Hide Caption 2 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Syrian artist Sedki Al Imam fled his hometown of Aleppo in 2012, eventually finding a home with his wife in Uppsala, Sweden. "It's heartbreaking," he says of the fighting between Syrian regime forces and rebel groups near Aleppo this week as peace talks were put on hold. The death toll rises as rockets, bombs and airstrikes pound already-beleaguered cities. Hide Caption 3 of 10 Photos: Blueprints of war: Syrian artists paint the struggle An anonymous anti-war artist whose Facebook handle is DAALI has a series of works captioned, "If it's not happening in your country that doesn't mean it's not happening." Many of them reference scenes of oppression in from Syria transferred to a Western event or location. In this case, women wearing niqabs and gloves -- clothing forced onto them in ISIS-controlled areas -- march on a fashion runway. An ISIS flag hangs in the back. Since the emergence of the Islamic State in Iraq and Syria, reports of rape, slavery and extreme oppression have filtered out of the group's tightly controlled territory. ISIS also claims more than 100 female foreign recruits, the majority of them from Europe. Hide Caption 4 of 10 Photos: Blueprints of war: Syrian artists paint the struggle The war has destroyed Aleppo, like other parts of Syria, artist Jawad says. It's now divided, with rebels controlling one side and the government the other. Barrel bombs pound the streets of a city that was once the most populated of the country. An estimated 300,000 civilians remain in rebel-held areas alone. Jawad says of this image: "Aleppo Citadel as I saw it in the midst of one of my nightmares. A once stunning, historical world-renowned structure is now sitting among utter destruction." Hide Caption 5 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Raised in the Alawite stronghold of Latakia, Wajdi Saleh also spent time in Aleppo, where he traces his roots and went to university. Forced to flee to Turkey a few years ago, he still wants to focus on the effect of Syria's civil war on the people who have not left and cannot leave. Referring to the rebel-held town of Douma, he paints its name in blood, in Arabic, on a wall. The date refers to August 16, 2015, when more than 80 people were killed during multiple airstrikes by the regime. An activist told CNN at the time: "Dead human bodies were just left on the sidewalk." Hide Caption 6 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Designer Saif Aldeen Tahhan is one of the thousands of refugees who made a treacherous journey across the Mediterranean Sea to get to Europe. Now, safely in Denmark, he designs pieces about the situation at home in Syria, one of them reflecting on the recent news out of Madaya. The rebel-held Syrian town's plight grabbed the attention of the world early this year as images of starving children, women cooking grass, and emaciated residents populated news feeds from smuggled videos put out by activists. Aid deliveries were finally allowed into the town mid-January, but people are still starving. Hide Caption 7 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Sedki Al Imam in his own words: "As different media outlets have always portrayed a good and an evil side in the ongoing Syrian crisis, 'Kingdom of Hyenas' aims to draw a truer picture of the Syrian war. It depicts all fighting factions as monstrous creatures, mercilessly killing innocents, and stealing everything they lay their hands on. It also most importantly compares Syria to a jungle, where justice, morality, and dignity are unheard-of, and the powerful feed off the blood of the weak." Hide Caption 8 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Artist Jawad no longer lives in Syria, though he says he is "Syrian by kismet," having lived through the rise of President Bashar Al-Assad's rule prior to the demonstrations and subsequent civil war's beginning, in 2011. Like the majority of Syria, Syria's conscripted army was mostly Sunni Muslim. At the start of the war, opposition groups accused the regime of killing more than 1,300 Syrians in first three months of the war. The "military boot has become a despicable national icon in Syria," Jawad says. "It squeezes and steps on our last surviving blood orange, the Syrian people," he adds. Hide Caption 9 of 10 Photos: Blueprints of war: Syrian artists paint the struggle Anti-war anonymous artist DAALI focuses his work on Syria so the world does not ignore it just "because it is not happening in their countries, because the dead people are not their families, because the destroyed houses are not theirs, because the women raped are not their wives, simply because they are just not living there." More than 4.5 million Syrians have left their homes, the majority of them having fled to neighboring countries. Many live in tents or container homes with no running water and seldom access to electricity -- in stark contrast to their lives at home. Few have the chance to move into the cities and continue their lives. Hide Caption 10 of 10

Cash flow problems

The documents detail how ISIS fighters are being paid, with fighters receiving additional stipends for their wives, children and sex slaves.

The average fighter is receiving "$50 a month, with an additional $50 for each wife, $35 for each child, $50 for each sex slave, $35 for each child of a sex slave, $50 for each dependent parent, and $35 each for other dependents," according to the document.

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Al-Tamimi said in the report that he received confirmation of these pay scales through conversations with ISIS-linked fighters during a visit to Syria.

The internal directives also call on ISIS fighters to reduce their electricity consumption and to stop driving official vehicles for personal use, a curbing of "perks" al-Tamimi said was indicative of an organization under financial strain.

Documents obtained earlier had shown that ISIS members stationed in Raqqa, Syria, ISIS' de facto capital, had to undergo a 50% pay cut.

Manpower shortages

Perhaps even more troubling for ISIS, the documents indicate that the organization is struggling to field adequate troops.

Al-Tamimi's paper said that the internal records show failed attempts to call-up additional fighters in the wake of defeats at al-Shaddadi in northeastern Syria and during the battle for Palmyra in central Syria.

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Al-Tamimi also noted that in October, ISIS had "issued a general amnesty for deserters" in a bid to bolster its ranks.

The manpower shortage was fueled in part because ISIS fighters were trying to get fake notes from doctors in order to get out of combat, according to some records.

But these ISIS fighters might find such notes hard to come by, as al-Tamimi also said that the Islamic State was facing a "medical brain-drain" as doctors flee ISIS-held territory due to mistreatment by the terrorist group.

Despite these shortages, al-Tamimi and other experts do not envision a widespread revolt against ISIS. "Populations under Islamic State rule are accustomed to poor living standards, exacerbated by years of civil war, and will likely stomach further decreases in quality of life for the time being rather than rebel and risk a brutal crackdown," he wrote.

Gersten said, "The men and women of the coalition are fighting every day to destroy this cancer, but we also must understand that this fight requires both patience and time."