The US-led coalition has killed 18 Islamic State leaders in the past 30 days, according to Operation Inherent Resolve spokesman Colonel John Dorrian. Thirteen of them were based in or around Mosul, Iraq.

Dorrian briefed the press on the airstrikes yesterday, saying that the deceased jihadists “were part of their [the Islamic State’s] military intelligence communication networks in Mosul.”

The airstrikes “have targeted military commanders, administration officials, foreign fighter facilitators, amirs, security commanders, communication leaders, and senior shura council leadership,” Dorrian said.

Three of the leaders were from Chechnya, highlighting the key role foreign fighters play in the Islamic State’s chain of command.

“In a two-day period in Mosul, we removed Abdul Hamid al Shishani, Abdul Jabir al Shishani, Abdul Rahman al Shishani, all Daesh [Islamic State] Chechen foreign fighters responsible for administration in command of fighters in Mosul,” Dorrian said.

Earlier this year, the US killed Abu Omar al Shishani, the Islamic State’s top Chechen leader in an airstrike south of Mosul. Shishani’s demise so close to Mosul demonstrated that the group had dispatched some of its elite fighting forces to the area in anticipation of the long-planned ground offensive to retake the city. Shishani’s death was celebrated by some al Qaeda figures on social media, as he was one of the central players in the rivalry between the Islamic State and al Qaeda that broke out in 2014. [See LWJ report, Abu Omar al Shishani killed south of Mosul, Islamic State says.]

The Chechens “hold kind of a special place within” the Islamic State, according to Dorrian, because they are “somewhat seasoned” and well-trained jihadis.

Dorrian identified Abu Jannat as another Islamic State leader who was targeted. Jannat was “an Iraqi native” and “responsible for military operations around Mosul, to include the manufacturer of chemical weapons in the defense of” the city.

The US has repeatedly targeted the jihadists responsible for managing the Islamic State’s chemical weapons program, as well as the facilities where the weapons are produced and stored. American airstrikes destroyed at least two such facilities in September. [See Threat Matrix report, US military hits another Islamic State chemical weapons facility in Iraq.]

The US-led coalition has also struck security personnel responsible for maintaining order in Mosul, which is one of the group’s two de facto capitals. According to Dorrian, one coalition airstrike is thought to have killed an Iraqi known as Abubakar, who was “an effective member of their leadership in [the] law enforcement apparatus.” Another bomb killed Abdul Ahmed Imara, who led the Islamic State’s “muta division,” which is “responsible for security in eastern Mosul.”

Thus far, according to Dorrian, there is no indication that the jihadists are planning to retreat from Mosul. “They show no signs of really trying to leave Mosul at this point,” Dorrian said. “Really, what they’ve done is they’ve continued to dig in, build elaborate defenses and so we’re — we’re really ready for a tough fight there.”

The US estimates that Abu Bakr al Baghdadi’s men number somewhere between 3,000 and 4,500 fighters in Mosul. They are a “mixture of Iraqi and foreign fighters,” Dorrian explained.

For long-time followers of the war in Iraq, some of Dorrian’s comments may seem like familiar ground. “The people who replace these leadership figures have not established their bona fides with [Abu Bakr] al Baghdadi, his inner circle, and they are often not as seasoned as those they replace,” Dorrian claimed. “This is especially true around Mosul as the coalition continues to be a relentless in degrading and disrupting command and control of their fighters, softening their grip on the city and prepping the battlefield for the liberation.”

The US and its Iraqi allies repeatedly decapitated the leadership of the Islamic State’s predecessor organizations in an attempt to destroy the jihadists’ state-building project in Iraq. Senior jihadists such as Abu Musab al Zarqawi and Abu Hamza al Muhajir were killed but then replaced, as have been numerous middle managers and lower-level tacticians.

While targeted airstrikes and other counterterrorism operations undoubtedly disrupt the jihadists’ command and control, and can weaken the organization, high value targeting is only one component of a successful counterinsurgency campaign. Given time and the space to operate, groups such as the Islamic State have effectively replaced their fallen leaders in the past. The fight to clear and hold Mosul, as well as other territories under the Islamic State’s control, will likely prove to be more important for disrupting the group’s ability to regenerate in the future.

Thomas Joscelyn is a Senior Fellow at the Foundation for Defense of Democracies and the Senior Editor for FDD's Long War Journal.

Are you a dedicated reader of FDD's Long War Journal? Has our research benefitted you or your team over the years? Support our independent reporting and analysis today by considering a one-time or monthly donation. Thanks for reading! You can make a tax-deductible donation here.