Trudy Rubin: At the front with Kurdish forces

Iraqi soldiers stand guard at the entrance of the Nineveh base for liberation operations in Makhmour, about 175 miles north of the capital Baghdad, on Feb. 11, 2016.

MAKHMOUR, Iraq - From a fortified Kurdish hilltop bunker I could overlook the frontline town of Gwer and across the Great Zab river to stands of trees and derelict buildings where ISIS fighters are dug in. On Monday night, ISIS rockets whizzed over this bunker.

Several kilometers to the rear, framed by dusty hills, sits Black Tiger Camp, the spartan headquarters of Gen. Sirwan Barzani, the Kurdish commander of the Gwer-Makhmour region. The camp gets its name from the 1990s, when the burly, mustachioed Barzani led peshmerga fighters in their rebellion against Saddam Hussein and earned the nickname "Black Tiger."

After Saddam was ousted, Barzani became a successful businessman, but he returned to battle to fight ISIS. Now he is at the center of the action: Makhmour is also headquarters for the Iraqi army command in charge of leading the long-awaited liberation of Mosul, the heart of ISIS-occupied territory.

In recent weeks, around 3,500 Iraqi troops have moved up to the Makhmour front and many more will be arriving. Senior Kurdish and Iraqi officers confer here regularly, along with U.S. officers who provide coordination and assistance.

A successful Mosul operation is essential to the eventual destruction of ISIS. "Mosul is the head ," Barzani says. "If it stays, ISIS will stay as a state." But, when it comes to the impending offensive, the general is a very worried man.

His 15,000 peshmerga are responsible for the hottest sector, but he doesn't have enough weapons. "We still lack ammunition, heavy machine guns, antitank weapons, still no night weapons," he says.

The Baghdad government doesn't pay for Kurdish arms or provide salaries to their fighters, and the strapped Kurdish Regional Government is hard pressed to do so. The day I arrived, peshmerga were celebrating because they'd gotten paid for the first time in three months.

"We thank the Americans, but the weapons are not enough," Barzani says. "We are being attacked every night and I don't have enough mortars to answer them along a 120-kilometer front line." The Kurds are frustrated that Washington delivers heavy weapons to Baghdad but they are not passed on to the Kurds.

Barzani is also worried because he sees no clear plan for the offensive. "They say there is a plan, but we are still waiting," he complains. "There is no formal plan until now."

The general says he still doesn't know which Iraqi forces will lead the operation.

The Kurds, whose tough, motivated fighters have retaken the bulk of liberated territory, don't want to enter the Sunni Arab parts of Mosul. The Iraqi Counterterrorism Service, which includes the country's top security forces, recently helped liberate Ramadi. But, says Barzani, "I don't know if the CTS is in the plan."

Nor, complains the general, is it clear if the Iranian-backed Shiite militiamen of the Popular Mobilization Forces will take part. Leaders of these militias are keen to join the fight, but Kurds rightly believe their participation could lead to sectarian slaughter of Sunnis.

The biggest worry is whether the Iraqi army is capable of liberating the center of Mosul on its own. Army units fled when Mosul fell, and collapsed when ISIS took Ramadi, leaving huge stores of U.S.-made weapons to fall into ISIS's hands.

"I worry that they will leave weapons to Da'esh," he says, using the the Arabic acronym for ISIS. "No one gives us those weapons, but the army left them to Da'esh and we [had to] take them from Da'esh.

"This system is not cost free. I have lost 131 men."

U.S. officers who have recently been involved in the training of 23,000 Iraqi forces at five bases in Iraq proper and Kurdistan are more optimistic, in part because the 570 U.S. trainers have focused on lessons learned from past debacles. For example, current training includes maneuvering in urban areas, along with obstacle breaching and countering IEDs (improvised explosive devices).

"Fighting in urban areas is an incredibly important part of train and equip," says Col. Scott Naumann, of the 10th Mountain Division, part of the team at Makhmour. "Da'esh will be defeated only when Kurds and Iraqis are working together." The joint command center at Makhmour, he adds, "is designed to help facilitate the relationship between Kurds and Iraqis and build trust."

But conversing with Barzani, it quickly becomes clear that building trust is still a work in progress. All the more so when the Iraqi government funds Shiite militias that are proxies for Iran, but still refuses to pay or arm the peshmerga, who stopped the ISIS advance in 2014.

It will be disastrous if Baghdad attempts a Mosul operation prematurely - before it addresses the concerns raised by Barzani, not to mention the question of who will secure multiethnic Mosul after ISIS is ousted. There is good reason why the head of the Defense Intelligence Agency, Lt. Gen. Vincent Stewart, recently told legislators that a Mosul operation shouldn't happen this year.

As I departed Camp Black Tiger, Barzani was joining a caravan of 20 SUVs that included U.S. and Iraqi officers and was headed to a meeting at the Joint Operations Room. Hopefully, U.S. advisers will put the brakes on any effort by the Iraqi army to mount an offensive too soon.