Five years after its president declared a war on Mexico's drug traffickers, a two-day Guardian series of articles and interactives assesses the scale of carnage that on average kills someone every hour. In this first piece, we look at Acapulco, the tourist haunt now haunted by fear, death and countless acts of brutality

Acapulco's bay sparkled and the big hotels that line the beach glinted in the sunlight in the view from Marino Casiano's tiny flat high in the hills above the resort. But the taxi driver's gaze was inward, clinging to the last shred of hope that his teenage son, abducted by gunmen in March, was still alive.

"I want to believe that they took him to recruit him into organised crime and took him somewhere else in the country to fight," he said in a tone of controlled despair. "Either that or he is in a clandestine grave."

Life for Casiano and the majority of the city's 780,000 permanent residents has always diverged from the image of unbridled fun the resort seeks to project. But life scraping by on the edge of the tourism economy is now also shrouded in the personal tragedies, pervasive fear, and additional financial woes associated with one of the major fronts in Mexico's drug wars.

"I blame the president," Casiano said. "What is the use of attacking the drug traffickers and bringing down capos [drug lords] if there are always others to take their place? If things get worse for ordinary people?"

Five years ago on Sunday, President Felipe Calderón kicked off his presidency by declaring an offensive against the drug cartels whose escalating turf wars along a major cocaine supply route north had started to become a real problem in a few areas of Mexico. But in the five intervening years, the military-led onslaught has served only to multiply the carnage. At least 46,000 people have been killed – one an hour – making some Mexican cities among the deadliest in the world.

Calderón remains defiant in the face of growing criticism of his strategy. "We are going to continue defending the citizens until the last day of my term," he said at an event to mark the fifth anniversary of his government last week. "Those who say that it would have been better not to confront the criminals are completely mistaken. If we hadn't done this, they would have advanced in our communities and our institutions."

Feeding corn on the cob to her three-year-old child outside their home in one of the poor barrios that line the road to the airport and the motorway to Mexico City, Marley is unconvinced. "The president says the good people outnumber the bad people but that isn't true," she said. She did not want her surname revealed for fear of being identified. "I see more bad people every day and I don't trust anybody anymore."

On at least five occasions, the young woman said, she had had to bundle her children indoors when armed groups started shooting at each other or at the police. Two months ago she was caught in the middle of a gun battle while at the market, and had ran for cover in a shop.

Then there are the bodies dumped on the ground and hung from bridges, the severed heads left in prominent places for all to see.

"If we are ever able to save the money up for the journey we will leave," Marley said, nodding at the little stall of T-shirts she sells. "It's not good for the children when they can tell the difference between fire crackers and guns."

Acapulco's turf wars are a particularly extreme version of the general trend of cartel fragmentation prompted by second-tier figures fighting over the spoils left by capos who have been arrested or killed.

According to Eduardo Guerrero, a drug war expert, there were six cartels when the offensive began. Now there are 16. Of these, he believes, only the Sinaloa cartel, the Zetas and the Gulf cartel have the capacity to traffic drugs internationally on any scale. The rest concentrate on kidnapping, extortion rackets and controlling local drug user markets. They tend to be particularly violent as they seek total control of the territories in which they operate.

"The fragmentation of the cartels is the product of the initial strategy of going after the cartelsm without any prioritisation," he said. "The government did not realise the problems this would bring with the dispersal of the violence."

The three most visible groups in Acapulco are the Independent Cartel of Acapulco, the Barredora (which means mechanical street sweeper in Spanish) and the Devil's Commando. All stem from the Beltrán Leyva cartel, itself a split from Sinaloa in 2008 that went on to divide again after its top leader was killed in December 2009.

The battle for control of Acapulco escalated after the arrest this August of the faction leader who held together the structure in the resort. The three groups fighting over it are believed to have loose links with other organisations, in particular Sinaloa, though others including the Juárez cartel, La Familia and even the Zetas are rumoured to be fluttering on the fringes of the conflict.

The bloodbath reached a peak in August when, local officials say, 148 people were killed during the month and the year's total was approaching 1,000. The door of the morgue was plastered with appeals to help find the missing, whom the authorities largely ignore.

By that time the bloodbath had spread out of the poverty-stricken outskirts into the main tourist area along the beach – a disaster for the resort, which is still a mainstay for national tourism despite the lost glamour of the days when Elizabeth Taylor regularly brought her entourage to town.

The local authorities say hotel occupancy rates remain healthy, but admit restaurants and bars have suffered acutely as holidaymakers rarely stray from their hotels into streets left empty by an informal sundown curfew.

The federal and state governments launched a major operation in early October, filling the city with 2,500 members of the army, navy and federal police, as well as 600 state police and a battery of equipment to add to the 1,500 local police officers. The official daily death toll has fallen from 3.6 in the two months before the operation to 1.6 in the same period after it, and the operation is now touted as a great success.

But will it last? In Ciudad Juárez, a surge in the military presence in the spring of 2009 saw a similar period of relative calm. Then the violence got worse than ever and established the border city as the most violent front of all.

The Acapulco operation claims to have learned from the mistakes of the past. It boasts an unprecedented level of co-ordination between the different forces, and promises more sophisticated efforts to clean up local police riddled with corruption, as well as social programmes aimed at stopping the young and poor getting pulled into organised crime. "Otherwise things become like Penelope waiting for Ulysses," said a spokesman, Arturo Martínez. "What you weave in the day, you unpick at night."

But while there is cautious optimism in the city centre where the holiday atmosphere is beginning creep back, scepticism is rife in the barrios.

"This whole thing is a pantomime to keep the tourists happy but for people like us it will get worse again soon," said Juana, 58, as she rocked her coughing grandchild in a hammock in the tiny shop where she sells homemade piñatas. "The kids going around with guns are getting younger every day."

Juana, who did not want to give her full name, got caught in the middle of a shootout inside the jail in June when she was visiting her son, who is serving a sentence for robbery. "If they can't even control the prison, how do you think they can control what happens outside?"