The U.S. military is planning to expand the number of so-called “fire bases” in northern Iraq to prepare for an assault on Mosul, ISIS’s Iraqi capital. The bases will be there to support local Iraqi forces. But they’ll also put U.S. troops near the front lines of what will likely be the biggest battle of the war with the self-proclaimed Islamic State.

Troops at up to three temporary bases, on the north-south route from central Iraq to the northern city of Mosul, would advise Iraqi security forces, provide logistical support so Iraqi troops can move toward Mosul and even ground base support fire, defense officials told The Daily Beast.

The movement of U.S. troops within miles of the ISIS’s Iraqi capital would be yet another indication that the American military is increasingly conducting offensive operations even though President Obama has never publicly acknowledged the U.S. is back at war in Iraq.

On Wednesday, the Pentagon began sending out signals that the U.S. role in Iraq could change, one day after the president led a meeting with his top national security advisers about the war.

In a briefing with reporters, Rear. Adm. Andrew L. Lewis, the Joint Staff’s Vice Director for Operations, said the U.S. is considering “accelerating the campaign against ISIL,” the government’s preferred acronym for the terror group.

One way, he said, would be by adding more bases.

“As Iraqi security forces progress toward isolating Mosul, there may be a situation in which there is another base,” Lewis said. “Their mission is to provide fires and support of Iraqi forces, just like we do with airplanes, just it’s surface-to-surface fires [versus] air-to-surface fires.”

The U.S. military often compares such shifts to the 20-month air campaign, in which U.S. troops launch strikes in support of local forces. But of course, ground forces are much closer to harm’s way.

Currently, near Mosul, there is one such U.S. base near the Iraqi city of Makhmour, Iraq, where roughly 200 Marines serve and where one Marine, Staff Sgt. Louis Cardin, was killed in an ISIS rocket attack. The base sits 70 miles south of Mosul and serves as a staging area for the Iraqi forces. U.S. officials renamed the base Kara Soar Counter Fire Complex after Staff Sgt. Cardin’s death.

The new name notably did not include the word “base,” as some Iraqis fear the return of any U.S. footprint that resembles the eight-year war that began with the 2003 invasion.

The U.S. military proposal to expand the number of —well, let’s call them “outposts”—is still in its preliminary stages. And it is short on the number of U.S. troops needed and how soon. Moreover, the Iraqis have yet to make significant advances toward Mosul that would demand U.S. help. They are about 65 miles away from the ISlS stronghold.

“It depends on what the Iraqis need,” one official explained.

The plan to move so many troops close to the fight is just another sign that the Iraqis cannot take Mosul without heavy U.S. assistance.

Part of the planning challenge is that the Iraqi security forces are trying to clear a number of cities before what could be a months-long Mosul offensive. On Wednesday, the Iraqi security forces were still engaged in heavy fighting against ISIS in the central Iraqi city of Hit, in what many hope will be the final day of that fight. U.S. military officials suggested Iraqi troops could battle for the city of Fallujah next, But it remains unclear whether the Iraqi military can reclaim that many cities, hold them and still push forward into Mosul.

The Iraqi military is training the divisions that would be tasked with moving from central Iraq north toward Mosul, the defense officials said. Kurdish forces would simultaneously move east to reclaim Iraq’s second-largest city.

Up until the Marines arrived in Makhmour to support members of an Iraqi division, the Iraqis had failed to advance toward Mosul. Indeed, some Iraqi troops hid from ISIS attacks in the nearby mountains. About a week after the Marines’ arrival, the Iraqis took control of three largely abandoned villages.

It appears the Iraqi Army has since lost one of those villages, stopping their push toward Mosul.

There only are believed two such support bases in Iraq. When asked if there were any other bases than the two the U.S. military already has acknowledged, Lewis said: “Not to my knowledge.”

The U.S. could close the one other such base, al-Taqaddum, in the country’s restive Anbar province, and move it north to bolster the U.S. effort in Mosul, one of the defense officials explained.

The Obama administration already is weighing a plan to sending hundreds more Special Forces to bolster U.S. efforts to search for potential targets, according to Reuters. On Tuesday, the president met with key members of his national security team to discuss potential changes to the U.S. strategy.

In recent weeks in Syria, ISIS has lost several cities—some to Russian forces, some to Syrian government troops, and others to U.S.-backed coalition forces. The rapid succession of losses, coupled with an ISIS that eventually walked away from a fight in each city, has buoyed U.S. hopes of taking back Mosul, one of the two most important cities to ISIS’s caliphate, the other being the Syrian city of Raqqa.

The fall of Mosul “would mark the beginning of the end for ISIL,” Army Col Steven Warren, a coalition spokesman, said on CNN Wednesday.