Soon after then-Lt. Gen. Charles Brown Jr. (center) became Combined Force Air Component Commander for Operation Inherent Resolve in 2015, he pressed to expand airstrikes from close air support missions to attack deeper into Islamic State territory, focusing on banks, command and control nodes, and oil transportation targets. He also sought to push authority to approve strikes down to the colonel level, enabling faster response. USAF
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Gradualism to a Fault

March 26, 2021

The air war against ISIS started slowly. Then strategic air power changed how the war was waged. 

At the end of 2011, against the unanimous urging of his main security subordinates not to do it, President Barack Obama summarily withdrew the last remaining U.S. occupation troops from Iraq to honor a long-standing campaign pledge. Those troops had provided an effective stabilizing presence in the country after nine years of slow recovery from the near-devastating insurgency that followed the three-week U.S. invasion in 2003 to topple Saddam Hussein. 

Rather than disentangling the United States from the region, however, Obama soon found himself stuck with a new war—and not just in Iraq, but also in neighboring Syria. This time the fight was against the self-proclaimed Islamic State in Iraq and Syria (ISIS), an abhorrent jihadist movement that arose in ungoverned spaces that opened up in 2012 as a result of the ongoing Syrian civil war. 

Operation Inherent Resolve (OIR) was slow to get started, and also was slow to show significant progress. The Obama administration did not respond to ISIS’ manifold abuses of hapless civilians until Aug. 8, 2014, and even that belated response was limited to airstrikes by U.S. Navy F/A-18s against a few ISIS positions in the northernmost portion of Iraq, near Erbil, where the American consulate and a substantial U.S. diplomatic presence were located. 

Targeting ISIS’ control, infrastructure, and governing hierarchy enabled the Air Force to move from supporting ground forces to disrupting the activities of a would-be state.

The U.S.-led air offensive continued for more than a year, primarily focused on tactical close air support, but repeated terrorist outrages perpetrated or inspired by ISIS worldwide finally forced the administration to expand its roster of approved targets in 2015 to include ISIS command centers and oil-bearing trucks, which brought in black-market revenue for the would-be caliphate. As two U.S. Air Force intelligence officers, Majors Michael Kreuzer and Denis Dallaire, later recalled, “while previous operations were primarily in support of coalition ground units fighting ISIS forces,” U.S. Central Command (CENTCOM) now allowed “deliberate strikes aimed at infrastructure, logistics, and governance nodes deep within ISIS-held territory.” 

This effort sought to target “the control, infrastructure, and governing hierarchy of a state,” which is essentially what ISIS was on a fast track to becoming. More important, the shift “enabled the Air Force to move from a role as a supporting entity for ground forces to one focused on discovering and disrupting critical ISIS support networks necessary to organize, train, recruit, and execute the group’s strategy.” 

The main mover behind this change was CENTCOM’s second successive Combined Force Air Component Commander (CFACC) for OIR, then-Lt. Gen. Charles Q. Brown Jr., who assumed that position in June 2015—10 months after the air war began. Today, Brown is the Air Force Chief of Staff.

As the chief of his Combat Plans Division, Col. (now Brig. Gen.-select) Jason M. Rueschhoff, would later recall, “General Brown was the impetus behind this moving of the fight deeper, focusing on strikes beyond the Army’s fire support coordination line (FSCL) and understanding the reality of what the ground forces needed in the near-term—[on-call close air support, or CAS for short]—as opposed to what they would need in the longer term, which was deep air interdiction against the most lucrative ISIS targets.” 

Not long after, the administration deployed U.S. Special Operations Forces (SOF) teams to support the indigenous Iraqi Security Forces and anti-regime Syrian Defense Forces, who had been fighting ISIS on the ground. It also authorized more strikes on identified ISIS leaders and on ISIS-controlled oil production facilities, which provided the jihadist movement’s main financial lifeline. In November 2015, U.S. and coalition aircraft dropped 3,227 bombs on ISIS targets, a new high. It followed with 3,139 in December, perhaps half delivered by B-1 bombers that could loiter over the battlefield for 10 to 14 hours with the help of multiple in-flight refuelings. 

Air assets were used to go after ISIS’ revenue. A pilot of a B-1B bomber, like this one shown flying with a French-manufactured Qatari Mirage 2000, recalled an attack on a bank in Mosul, cracking its safe and sending a “plume of burning currency nearly 100 feet into the air.” Staff Sgt. Clayton Cupit

One B-1 aircraft commander recalled “some dramatic changes as we began targeting ISIS revenue.” One target “was a bank in Mosul containing millions in currency that was being used by ISIS to pay its fighters,” this pilot and Weapons School graduate said. “We did our best to quickly devise an optimized delivery solution in the jet using two GBU-31(V)3 Joint Direct Attack Munitions. The resulting impacts not only cracked the safe but also sent a plume of burning currency nearly 100 feet into the air.” 

Despite such examples of aircrew flexibility at the tactical level, CENTCOM’s broader effort had yet to attain the magnitude of a bona fide campaign. While Obama sought to characterize the intermittent bombing as “a systematic campaign of air- strikes,” the action still lacked a well-defined strategy aimed at seeking achievable goals on a realistic timetable. On the contrary, its mission statement remained vague: to “degrade and ultimately destroy” ISIS.

Obama’s halting counteroffensive took more than a year to reach a point where the rules of engagement (ROE) relaxed sufficiently for planners in Air Force Central Command (AFCENT) to consider a finite number of possible civilian casualties per target attack if those casualties were deemed proportionate to the assessed importance of the target. Until then, AFCENT was “tied up in obsessive platinum-standard target vetting” dictated by White House-mandated ROE that were, according to Washington Institute analyst Michael Knights, “without a doubt the most obsessively restrictive of any air campaign ever fought by a U.S. coalition.”

Indeed, throughout OIR’s first year, final authority to approve any strike that might result in significant civilian casualties remained at the four-star level in CENTCOM’s headquarters at MacDill Air Force Base, Fla. Not until September 2015 was CENTCOM finally allowed to delegate greater target engagement authority down to the forward-deployed Combined Joint Task Force (CJTF) commander for OIR in Kuwait, U.S. Army Lt. Gen. Sean B. MacFarland, who, in turn, pushed it down to his subordinate one-stars who oversaw the task force’s two Combined Joint Operations Centers, or “strike cells,” in Baghdad and Erbil.

It took another year before the next CJTF-OIR commander, U.S. Army then-Lt. Gen. Stephen J. Townsend, delegated targeting authority to his colonels in the two Army-dominated strike cells. With that, the number of officers in the kill chain who could approve strikes finally was great enough to ensure round-the-clock approvals from the strike cells. 

Reprioritizing Air Power

From the time he assumed command of the air war in June 2015, Brown worked aggressively to streamline the target approval process, seeking better inputs from the Intelligence Community, and adding more important targets, such as ISIS cash reserves and oil-related facilities, to the daily list generated by the Combined Air Operations Center (CAOC). Up to that point, most of the mission lines flown in AFCENT’s daily Air Tasking Order had been devoted to providing dedicated combat air patrol (CAP) orbits intended to be on call at a moment’s notice for indigenous friendly ground troops, irrespective of what might have actually been required in the covered area. 

Such daily CAPs came to be regarded as a given by CENTCOM’s land component, Brown’s chief of combat plans said. Yet with limited air assets available, they were in direct competition with other requirements, such as deeper strikes against the enemy’s key nodes. Eventually, he said, “as target sets began to emerge through discovery and development, a prioritization took place in the CAOC on how we allocated air to provide close air support, when needed, and interdiction.”

The chief planner continued: “Although the concept wasn’t new, the thought was to look at the problem differently than had been done with counterinsurgency air support operations in Iraq and Afghanistan. In the end, we began pulling strike assets off of traditional 24/7 CAS CAPs, either moving the CAPs to locations where expected ground contact would occur or else moving them where they could still respond quickly, but now to multiple areas across Iraq and Syria. We could then cover more area … while still retaining our deeper strike capability.” 

Brown’s approach was almost an exact replica of then-Lt. Gen. Charles A. Horner’s novel concept of “push CAS” used in 1991’s Operation Desert Storm, despite initial opposition from CENTCOM’s Army corps commanders. That concept assured those subordinate land commanders that they would have all the CAS they needed if required, but without needlessly tying up coalition strike aircraft for on-call CAS throughout the theater.     

Brown later recalled that not long after he arrived at Al Udeid [Air Base, Qatar] as OIR’s second successive CFACC, “CJTF-OIR developed a battlefield geometry that designated portions of western Iraq and eastern Syria as battlespace assigned to the CFACC. This was helpful in pushing for deliberate targets beyond the land component’s FSCL and CAS mentality. The challenge was within the CJTF’s intelligence, surveillance and reconnaissance (ISR) allocation process, in which ISR and other capabilities were apportioned against various ‘named’ subordinate operations across the CJOA [combined joint operating area].” Though not used for OIR to that point, Brown said, the process had been used earlier for Operations Enduring Freedom and Iraqi Freedom. “I pushed for a comparative and transparent analysis of organic CFACC-provided theater ISR allocation and apportionment across the CJOA, clearly illustrating the limited ISR allocation and apportionment to deliberate target development,” Brown recalled later. “This resulted in a more fulsome discussion of the balance of ISR between the close CAS fight and deliberate targeting efforts.”

Coalition fighters like this F-15E destroyed 186 ISIS oil tanker trucks on Dec. 8, 2016, depriving ISIS of an estimated $2 million in revenue. The attack was only possible once air resources were shifted from almost exclusive focus on close air support missions. Staff Sgt. R. Alex Durbin

When U.S. Air Force F-15E Strike Eagles put eight precision munitions into a bank containing millions of dollars worth of ISIS cash reserves on Jan. 18, 2016, it was a telling testament that AFCENT’s performance had finally begun to show signs of perceptible gains in strategic effectiveness. By the spring of 2016, airstrikes had reduced ISIS’ oil production by some 30 percent, having destroyed more than 400 oil tanker trucks. Revenue from black-market oil sales had been reduced by as much as half. On Dec. 8, 2016, coalition fighters destroyed 186 ISIS oil tanker trucks that had been concentrated in the open near Palmyra, Syria, inflicting an estimated loss of more than $2 million in illicit revenue. 

Brown freely acknowledged that, as a result of more than a decade of near-exclusive concentration on providing on-call CAS to beleaguered friendly ground troops, the professional staffers in the CAOC had all but forgotten the complex art of assessing which fixed targets were of greatest importance to the enemy. This required an almost overnight shift in emphasis from so-called dynamic, or real-time, targeting of emerging objects of fleeting import, like ISIS vehicles, to deliberate targeting of larger fixed and known enemy assets, such as headquarters buildings and oil storage facilities, whose elimination might promise more enduring strategic results. 

For their part, the expert targeteers in AFCENT’s rear-area headquarters at Shaw AFB, S.C., had continued to conduct painstaking deliberate target analyses and to prepare meticulously documented financial and oil-related target folders as far back during the campaign as early 2015. Such deliberate target-attack options relied on a systematic accumulation of overhead imagery, electronic intercepts, and informers’ tips that all pointed to sites for immense holdings of ISIS cash reserves in bank vaults, private residences, and elsewhere. Requested strikes against those choice targets, however, had invariably been disapproved by the Obama White House out of concern over potential civilian fatalities. 

Tellingly, Brown remarked in July 2016 that his “biggest accomplishment” since becoming CFACC had been reintroducing more sophisticated targeting capability. “In the last 15 years or so, we’ve done a lot of close air support for troops in contact and armed overwatch, and in the deliberate targeting process, we lost a little muscle memory from what we had in the past,” Brown recalled. “So I think this is something that’s going to help us in CENTCOM’s area of operations and in other contingencies later on that we, as a nation or as the coalition team, may face in the future.” CENTCOM also fielded a modest number of additional U.S. SOF teams to work with indigenous friendly ground forces. As a result, the intensity of aerial weapon deliveries against ISIS grew steadily, from fewer than 200 a month in August 2014 to more than 3,000 a month by mid-July 2016. These changes helped shift ISIS to the defensive for the first time since its emergence as a would-be caliphate more than two years before.

By November 2016, as the move by the Iraqi Security Forces to retake Mosul began gathering headway, a stack of 43 coalition aircraft orbiting overhead and on call as needed to provide both direct attack and CAS included B-52s, AV-8Bs, F-15Es, and F-22s, all holding on station and ready to engage any emerging targets as they were called out by Joint Terminal Attack Controllers (JTACs) on the ground. Those JTACs, in turn, were aided by more than a dozen remotely piloted aircraft, including armed Predators and Reapers, which provided real-time, streaming target video imagery. That aerial armada offered a glimpse at the magnitude to which AFCENT’s air effort had finally grown.

From a bigger-picture perspective, however, the air war was still only marking time. True, the number of strikes against ISIS targets was up by 65 percent over a year before, and ISIS’ recruitment of new jihadists was thought to have decreased from around 1,500 a month at the height of the movement’s appeal to only 200 a month by early 2016. Nevertheless, the rate of daily airstrikes into Raqqa—ISIS’ avowed capital in Syria—remained limited even at a time when, after 21 months of bombing, some 12,000 attacks had been conducted in all against ISIS positions at an assessed total cost of $7 billion. 

Signs of Decay

Gradually, clear signs emerged that ISIS’ leadership was struggling. ISIS began publicly conceding to their rank and file that the movement was encountering declining fortunes on the battlefield and could well be soon facing an imminent collapse of their vaunted caliphate. Steadily shrinking terrain holdings in Iraq and Syria and the forceful ejection of ISIS from Fallujah by mid-2016, along with the progressive increase in the number of ISIS-inspired terrorist acts abroad, all joined to indicate ISIS’ faltering grip on its home turf. By that point in the air war, the bombing effort’s steady gains were a direct result of the increased number of munitions dropped on ISIS targets each month and of the expanded list of target categories now approved for attack. 

This came at a price. By the end of July 2016, the overall assessed cost of OIR had reached $8.7 billion, with coalition aircraft having conducted nearly 15,000 attacks on more than 26,000 individual target aimpoints. Yet the Iraqi Security Forces remained no closer than before to recapturing Mosul and depriving ISIS of its controlling presence in northern Iraq, because so many of the targets that had been struck were of little strategic import.  

Air Force Chief of Staff Gen. David L. Goldfein declared at the end of August 2016 that OIR was now “absolutely going in the right direction.” Yet Marine Corps Gen. James Mattis was no less on target when he offered the more sobering observation, at roughly the same time, that the administration’s effort against ISIS remained “unguided by a sustained policy or sound strategy.” 

Following the unexpected election of Donald J. Trump to the presidency on Nov. 8, 2016, Trump appointed Mattis his Defense Secretary, and having promised in the campaign to ramp up the war on ISIS, Trump gave Mattis room to maneuver. The limits that had been placed on warfighters were reduced and in December 2018, Trump declared ISIS defeated. 

High-value targets such as ISIS weapons bunkers became the focus of air attacks in 2016, after then-Lt. Gen. Charles Brown Jr. convinced higher-ups to ease restrictions on strategic bombing. USAF/courtesy

In the end, OIR turned out to have been another American and coalition success story made possible largely by air power, once freed from the shackles imposed by  Washington leaders who misread the enemy as a reborn Iraqi insurgency and consequently insisted on ROE meant for a different kind of war. It was that indispensible force element that finally allowed indigenous anti-ISIS troops who conducted the brunt of hard fighting on the ground with the help of embedded U.S. SOF teams and JTACs, to free Mosul and Raqqa in fairly close succession and ultimately to strangle the jihadist movement in its cradle. 

Throughout it all, the combat performance of the aircrews who conducted the effort at the execution level was invariably able and effective, reflecting the high standards of operator competence and professionalism displayed in Operation Desert Storm and subsequent U.S.-led air offensives. 

Yet the campaign was needlessly prolonged by two years or more thanks to its ill-conceived launch and its anemic first year. As a result, America and its coalition partners took as long to put away a fairly tractable low-technology enemy in the relatively bounded spaces of Iraq and Syria as it took the United States, in a total war for ultimate stakes, to defeat the vastly more powerful Imperial Japan and Nazi Germany in two major theaters on opposite sides of the globe in World War II.                            

Benjamin S. Lambeth is a nonresident senior fellow with the Center for Strategic and Budgetary Assessments and previously spent 37 years as a senior research associate at the RAND Corporation. This article is adapted from his new book, “Airpower in the War against ISIS” (Naval Institute Press, 2021).