A Kurdish fighter stands guard at a temporary military camp in Gwar, northern Iraq, as his colleagues train before deploying to fight the Islamic State. (Ahmed Jadallah/Reuters)

The army base in Iraq’s western Anbar province had been under siege by Islamic State militants for a week, so when a convoy of armored Humvees rolled up at the gate, the Iraqi soldiers at Camp Saqlawiyah believed saviors had arrived.

But this was no rescue attempt. The vehicles were driven by militants on suicide missions, and within seconds on Sunday the base had become a bloody scene of multiple bombings.

On Monday, a day after the attack, five survivors — including three officers — said that between 300 and 500 soldiers were missing and believed to be dead, kidnapped or in hiding. Army officials said the numbers were far lower, leading to accusations that they were concealing the true toll.

If the survivors’ accounts are correct, it would make Sunday the most disastrous day for the Iraqi army since several divisions collapsed in the wake of the Islamic State’s capture of the northern city of Mosul amid its cross-country sweep in June.

In any case, the chaotic incident has highlighted shortcomings in an army that the United States has spent billions of dollars training and equipping, and it has further undermined the force’s reliability as a partner as President Obama expands airstrikes into provinces including Anbar.

It has also heightened pressure on new Prime Minister Haider al-Abadi, whose opponents have already seized on the incident to accuse him of a soft-handed approach to terrorists.

While U.S. aircraft have carried out strikes in support of Iraqi forces in other recent clashes, there was no indication that any American airstrikes were made against these Islamic State attackers, other than unconfirmed reports from Iraqi officials. Accounts released Sunday and Monday by U.S. Central Command made no mention of the overrun Iraqi base.

The lead-up to Sunday’s crisis began a week ago, when the last road to Camp Saqlawiyah, just north of insurgent-controlled Fallujah, was cut by Islamic State militants. One of two tanks that were among the vehicles guarding the road left to refuel, and the militants took the opportunity to attack those that remained, said a 9th Division soldier who was present and spoke on the condition of anonymity because he was not authorized to speak to the news media.

The fall of the units protecting the supply route meant that the five battalions inside the base were completely besieged.

“There were no reinforcements, no food supplies, no medicine, no water, and then our ammunition began to run out,” said 1st Lt. Haider Majid, 28. “We called our leaders so many times. We called our commanders, we called members of parliament, but they just left us there to die.”

Soldiers said they sought help from Lt. Gen. Rashid Fleih, the head of Anbar Military Command. He told Iraq’s al-Sumaria news on Monday that the troops on the base were just complaining because they were trapped and “bored.”

Fleih said the army had delivered supplies while the base was under siege. But soldiers maintained that they received nothing, and thirst eventually forced them to dig a hole to dirty, salty water.

“Even if it was dangerous for helicopters, it was their duty to try to help us,” Majid said.

Survivors said they faced daily attacks during the week, including one using chlorine gas, a claim that was impossible to verify Monday. While some said colleagues had suffocated in the attack, Col. Ihab Hashem, the deputy commander of an 8th Division battalion, said canisters had fallen short of the base.

Attackers in disguise

The major assault came Sunday. Soldiers interviewed said army commanders had sent word via walkie-talkie that a rescue mission was on its way and had taken control of a nearby bridge.

Shortly afterward, Iraqi army armored vehicles and military trucks arrived, and the men inside were dressed in the uniforms of Iraqi counterterrorism forces, the surviving soldiers said.

“We thought this was the support we were promised was on the way,” said Capt. Ahmed Hussein of the 8th Division. “The first three Humvees were ahead of the rest with some military trucks. We just let them in.”

One Humvee exploded in the middle of the camp. The two others drove to the perimeter and detonated. The rest of the Islamic State convoy was held back at the entrance, where the survivors said the militants carried out several more suicide bombings as they tried to break in.

“I gathered my soldiers and said: ‘We are going to die anyway. Let’s try to get out,’ ” Hussein said, adding that he and about 400 other soldiers escaped under heavy fire in a convoy. Others were left behind.

Those who got away divided into three groups, eventually leaving their vehicles after some were hit by roadside bombs. They continued on foot, traversing nearly two miles of territory held by the Islamic State until they reached Camp Tariq, about four miles away.

“I was in the first group; there were about 150 soldiers in each,” Hussein said. “Only about half of each group made it.”

The rescue mission that the soldiers had been told was coming “100 percent failed,” he said. On the bridge that they were told had been secured, they found the remnants of that mission: burned army vehicles.

“No one knows how many people died,” said the 9th Division soldier, who spent days stranded in a house with 60 other soldiers. “We kept moving and never looked behind. Those who died, died. Those who were captured, were captured. We just ran for our lives.”

Hussein estimated that 250 soldiers died at Camp Saqlawiyah, and 100 to 150 are missing. Hashem put the number of dead and missing at 400 to 500.

But there were hopes that some might still make it back. A group of 13 has been in contact, according to Hashem, to say they are hiding in marshlands, another 13 in a grove of trees. He advised them to wait until the cover of night to try to make the rest of the journey.

Government’s response

The Iraqi Defense Ministry acknowledged Sunday that it had lost contact with some of its soldiers during the incident but did not say how many were missing. Fleih said that it was possible to “count them on one hand.”

“It looks like the Defense Ministry is trying to push the numbers down,” said Mithal al-Alusi, a member of the Iraqi parliament’s defense and security committee. “If we have lost people or not, this proves military structure and military strategy is not able to fight ISIS,” he said, using an acronym for the Islamic State.

He added: “Mosul they said was a surprise — what’s the excuse this time?”

Abadi, who also holds the position of commander in chief of the armed forces, issued a statement Monday saying army commanders would be interrogated on charges of negligence. The statement said the prime minister had ordered supplies to be delivered to the stranded soldiers four days ago.

For some soldiers, the incident was the latest — and last — in a series of humiliations. Hussein, for his part, said he would leave the army to join a Shiite militia.

“We don’t have any leadership,” he said. But for the militias, “their leadership is with them in the field; they look after their soldiers.”

Mustafa Salim contributed to this report.