During the most recent deployment of the Marine Corps' Middle East crisis response task force, small elements were quietly deployed to hot spots on the ground in Iraq, some close to the key Islamic State stronghold of Mosul, where a coalition fight to retake the city rages on.

In a debrief about the nine-month task force deployment, which ended in December, senior officers of Special Purpose Marine Air-Ground Task Force Crisis Response-Central Command discussed four different elements that were dispatched for specialized missions in Iraq, one for a secretive assignment at the behest of the secretary of defense.

That particular mission was known as Task Force Whiskey, an assignment the Marine unit received at the end of October 2016, from then-Defense Secretary Ash Carter. It called for a company-sized element of Marines inserted near Erbil, about 50 miles southeast of Mosul. The task force was tapped because the Marines were ready and available, Operations Officer Lt. Col. John Bossie said.

"We were the only one that could respond to it quickly enough to get forces into country, up near Erbil, to conduct that mission," he said. "The order came out about the 28th of October, and by the third of November, we had the first elements on the ground, conducting their [pre-deployment site surveys], getting the site set up, so we could then use our own organic air to fly the rest of the force in."

Just an hour from Mosul, Erbil is the capital of Iraqi Kurdistan, home to militia forces who have fought alongside the Iraqi Army to overthrow the Islamic State. The road connecting Erbil and Mosul has featured prominently in the fight to retake the ISIS-held city.

The commander of the crisis response force rotation and its 5th Marine Regiment headquarters element, Col. Kenneth Kassner, declined to go into detail about the precise mission of Task Force Whiskey, but said it was reconnaissance in nature. In total, the tasking lasted 90-100 days, officials said, putting it inside the threshold for temporary troop presence and meaning the Marines did not need to be counted against the U.S. troop force management level, or maximum end strength in the country.

"There were many occasions such as this one: A task would come through [U.S. Central Command] to [Marine Corps Forces Central Command], and as different forces then conducted their own feasibilities of support -- more often than not, it was the special purpose MAGTF, or in concert with our [Marine Expeditionary Unit] colleagues on the ship that were able to respond to these emerging crises now," Kassner said.

It's the first time task force officials have publicly discussed such missions in support of the anti-Islamic State fight, Operation Inherent Resolve. The task force, which operates in a half-dozen countries across the Middle East, has maintained a steady contingent of 100 troops at the U.S. Embassy in Baghdad for security, and has staffed U.S. bases in Al-Asad and Al-Taqaddum in central Iraq.

In spring 2016, a small contingent of Marines was dispatched to establish a new artillery position in northern Iraq, initially known as Fire Base Bell and then renamed Kara Soar Base. But these troops came from the deployed ships of the 26th Marine Expeditionary Unit, which, unlike the task force, had native artillery capabilities.

These more recent small and temporary detachments of Marines dispatched to execute ground missions may demonstrate a growing willingness of regional commanders to exploit the flexibility and availability of the task force in innovative ways.

In another example of such a mission, Bossie said, the task force was called upon to create an exploitation and analysis cell, staffed with military police and law enforcement Marines, to confiscate and process information left behind by Islamic State militants as they were flushed out of Fallujah by Iraqi and coalition forces last summer.

"As the clearance of Fallujah happened, a bunch of ISIS convoys were leaving Fallujah, and coalition forces struck the convoys as they were leaving," he said. "We were able to use our human intelligence Marines as well as this exploitation-analysis cell to collect thumb drives and hard drives that came out of those convoys."

In the single convoy strike, Bossie said, Marines harvested 80 gigabytes of data, the rough equivalent of 800,000 documents.

"So that then became something that [Combined Joint Task Force-Operation Inherent Resolve Commander Army Lt. Gen. Stephen Townsend] notices," Bossie said. "So we then forward-postured that exploitation analysis cell in Taji and Erbil."

Taji, just north of Baghdad, houses an Iraqi Army training camp and air base, and has been the site of various Islamic State attacks. At both sites, Marines with the exploitation-analysis cell worked with special operations troops and conventional forces to use confiscated information against the ISIS militants.

"As the clearance of Mosul kicked off, those Marines were in place to exploit that captured enemy material and send it to higher intelligence authorities," Bossie said. "They went in initially for 90 days. They did such a great job, they got asked to stay for another 90 days. We left and they were still there, so I think there's going to be another extension before a national-level entity can get in there and take over."

Task Force Marines were also called upon to play an advisory and assistance role for troops from the 15th Iraqi Army Division while they staged at the Qayyarah West airfield prior to entering Mosul. The airfield, recaptured from ISIS troops in July 2016, would by October become the international headquarters and staging location for the battle to retake the militants' primary stronghold in Iraq.

Again, Bossie said, the Marines proved their value with rapid organization and response times.

"In about 10 days, we launched a force. They were in Q-West initially for 90 days, but ended up staying for more like 180 days," Bossie said. "They provided advise and assist to not only the 15th Iraqi Army Division, but also the federal police, who were a large part of the clearance of Mosul. It's another good news story for the MAGTF."

This detachment was especially small: just 14 to 15 Marines, task force officials said. But a force nearly as compact was dispatched with little fanfare to the U.S. Embassy in Baghdad in June 2016 when spikes in kinetic activity and protests appeared to portend an attack.

The unit scrambled 24 Marines to augment the 100-Marine security force already on site, sending a mixture of infantrymen and law enforcement troops to ensure the force had training in non-lethal crowd and riot management.

"We task-organized a force using our own organic air, flew it into Baghdad, staged them, and under cover of darkness, slid them into the embassy," Bossie said. "When the sun came up the next morning, there were 24 more Marines standing a post, reinforcing that location."

The Marines stayed just seven to 10 days, he said, before the threat appeared lessened and the element pulled out again. Time from receiving the tasking to inserting Marines at the embassy: just four hours, 45 minutes, Bossie said.

In large part, the way the Marine Corps task force can be used in Iraq and elsewhere to fight ISIS is limited only by the pertinent commanders' creativity.

In response to questions from Military.com, officials with Combined Joint Task Force OIR, which oversees the coalition fight, said there had been no change to policy or strategy regarding manning or force employment.

"The coalition commander maintains a wide range of capabilities at his disposal," an official said in a statement. "All of these are considered in our plans to defeat ISIS in Iraq and Syria."

The official added that CJTF-OIR operates in Iraq at the invitation of, and in coordination with, the government of Iraq.

While all of the Marine Corps detachments, with the possible exception of the exploitation-analysis unit, remained on the ground 180 days or fewer and thus did not count toward the Iraq force management level, employment of task force Marines may become even more flexible in the future.

In late April, the Pentagon confirmed that President Donald Trump had delegated to Defense Secretary Jim Mattis the ability to determine maximum troop levels as he sees fit, altering a troop ceiling policy frequently criticized as arbitrary and so full of loopholes as to be effectively meaningless.

Today, the battle for Mosul rages on, with Iraqi Army Chief of Staff Lt. Gen. Othman al-Ghanmi recently predicting the coalition force would see definitive victory this month.

A new rotation of Marine Corps crisis response troops is now in place in the Middle East, led by the California-based 7th Marine Regiment.

"This is a force that's purposely task-organized to conduct myriad missions," Kassner said. "Organically, we're able to bring these forces together, task-organize them, and organically move them across the battlespace. So we're a ready force -- ready now."

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at@HopeSeck.