On June 9, at around 3am, a team of marines was clearing a building in a bombed-out commercial district in Marawi city when all hell broke loose.

The room they had just stormed was suddenly on fire. Their enemies were throwing petrol and fuel bombs at them. The marines ran outside, only to land in a kill zone. They were pinned down by snipers, rocket-propelled grenades (RPGs), and mortar rounds.

Sergeant Sandy Benitez, 34, his left foot pierced by shrapnel, crawled along a short stretch of street for nearly five hours to safety.

Technical Sergeant Mahamud Darang's armoured carrier was with a column of troops sent to reinforce the embattled marines. But as soon as they crossed a bridge that led to the combat zone, they came under heavy fire. An RPG hit the ground in front of his vehicle. Sgt Darang spotted the shooter, on the third floor of a building, just before he fired again. The second round came right into his armoured carrier and blew up. Bleeding, the 21-year ordered his men to leave the burning vehicle and take cover in a nearby building.

The pitched battle that day lasted 14 hours. When the dust settled, 13 soldiers were dead. It was the biggest setback to government forces in the battle to recapture Marawi from Muslim militants who wanted to turn it into a "province" of the Islamic State in Iraq and Syria (ISIS).

Retaking that city was supposed to take just 10 days. But it has been over a month already, and the military has stopped setting deadlines. So far, 67 soldiers and policemen have been killed.

While the army controls most of the city, it continues to be held back by sniper fire and booby traps. The militants are also using dozens of hostages as human shields.

Experts say the battle for Marawi has taken this long because the soldiers sent there are used to conventional warfare in jungles and sparsely populated mountain villages, not in a city full of fortified buildings and multi-storey homes.

The militants who stormed Marawi on May 23, on the other hand, came prepared for a long- drawn siege.

Most of them grew up in Marawi. They knew the city. They knew where the chokepoints, tall structures, basements and tunnels were. They knew that most neighbourhoods, primed by decades-long clan wars, were teeming with firearms. All they had to do was knock or just barge in.

Young and steeped in radical Muslim ideology, they were highly motivated and prepared to die. They were not there for a pay cheque. They were there to fight for their beliefs.

The marines and scout ranger units sent to dislodge them, meanwhile, had just come out of months of fighting in jungles.

A battalion commander, who asked not to be named so he could speak candidly, told The Straits Times that most of the soldiers fighting in Marawi were not equipped for urban warfare.

"They didn't have gas masks, tear gas, night vision goggles and individual radios that will allow them to talk to each other," he said, adding that many units were clearing buildings without adequate body armour, smoke grenades and breaching equipment.

The army is simply not primed for urban warfare, he said.

"That's an organisational problem we have not solved by learning from past experiences. We have to retool, so that we can eventually respond to any urban setting."

Mr Elmer Cato, charge d'affaires at the Philippine embassy in Baghdad, told The Straits Times that the Marawi experience shows the "ISIS playbook" at work.

"The (militants) have not employed IEDs (improvised explosive devices) at the same level of sophistication ISIS uses them in Iraq, although we have seen the damage their RPGs have been able to inflict on government forces. This, of course, could change if Filipinos and South-east Asian and other foreign fighters who have trained and seen action in Iraq and Syria are able to make their way to the Philippines," he said.

Congressman Ruffy Biazon, whose father was military chief under the late president Corazon Aquino, said Congress would have to "reconfigure" the military's budget to give soldiers vehicles with thicker armour, more accurate attack aircraft and other equipment more suited for urban warfare.

"You see what's happening. It should not happen again," he said.