It is a wet winter Saturday on a muddy playing field in an unprepossessing part of south Manchester. The river Mersey slides past behind a row of trees planted to provide shelter from the wind, chill gusts cutting through the gaps where saplings were torn out by local kids to sell on elsewhere.
On the pitches, children of every size are playing football: four- and five-year-olds being taught the game, three teams of under-nines, the same again of under-10s. Dogs are being walked, and dogs are being allowed to do what dogs naturally do. By the changing rooms, a woman collects subs of £2 a child, less if they have brothers or sisters playing and the extra cost would mean one of them missing out.
Old Trafford lies four miles and several worlds away, across the flat suburban streets of Stretford to the north-west. The Etihad Stadium is six miles to the north-east, beyond Rusholme and Ardwick, new oil-money-bright in an old coal town. And yet these council fields are the new front line in the battle for supremacy between United and City, and these kids – shivering, laughing, falling over and pushing past – are the trophies both clubs are fighting for.
The reasons are not hard to find. Inside the squat changing room, away from the damp patch on the ceiling where the flat roof leaks, a trophy cabinet spills its silverware on to shelves and filing cabinets either side. On the opposite wall are photos of the young-boys-made-good who won them.
Marcus Rashford, striker for United and England. Danny Welbeck, United, Arsenal and England. Wes Brown, Jesse Lingard. Ravel Morrison - made good, made bad, as innocent here aged eight as he would ever be.
A few years back, the sporting civil war in this city was played out in headlines and big statements. City, in the first flush of investment from Abu Dhabi, paying for a huge “Welcome to Manchester” billboard on Deansgate featuring the face of former United striker Carlos Tevez; United rising to the bait, Sir Alex Ferguson hitting out at the “noisy neighbours” and “a small club with a small mentality”.
Now, on the surface at least, all is calm. Neither club tends towards public grandstanding. Both have owners who prefer to remain in the background. Open hostility has been replaced by easy detente.
On the surface. Elsewhere – on playing-fields around the north-west, on school playgrounds, in classrooms and in back gardens - it is more intense than ever before.
There are the tiddlers, potential future players, seen by both as future customers.
There are the secondary school-age stars who move between each other's youth set-ups.
And there are the scouts and coaches – Dave Harrison, eight years at City, recently headhunted by United to do for the club's youth recruitment what he had done at City and Leeds before that; his former colleagues Ronnie Cusick and Lyndon Tomlinson, enticed across town to work alongside him.
“When City got their investment, when they built the Etihad campus, they were getting the best of everything,” says Dave Hobson, scout for United from 2001 to 2014, now head of the Professional Football Scouts' Association.
“We all had a meeting with Alex Ferguson. A bottle of wine on the table. And he always praised us for what we did.
A lot of cheques are being written. A large number City's part-time scouts and coaches are rumoured to have had their wages doubled. United have responded by hiring even more – men on the ground, coaches at their Aon training complex in Carrington, set out in the green lanes between the M60 orbital motorway and the M62.
“Scouts are the Cinderellas of a football club,” says Hobson, who at one point had a player of his in every age group at United from under-nines to the first-team squad. “They find the player, the agent finds out their address.
“Nobody can run a football club unless you've got scouts to bring the players in. You can't coach players if you don't have any.
“But it's become an arms race.”
St Bede's College is a 140-year-old private school in leafy Whalley Range, mid-way between Fletcher Moss and the Etihad. It costs £3,595 per term to have a child educated there.
City will now fund those fees for any boy signed to their academy, all the way through to GCSE exams, even if they are released at a younger age.
Many would see that as a good thing. Last summer the rate of A* or A grades at GCSE level at the school was 42%. Better to educate kids than to develop only their sporting abilities. Others says that it is too much of a good thing.
It is also an increasingly potent weapon. Twenty-five years on from the Class of '92, when United’s home-grown legion transformed the balance of power in English football, City's drive for young minds is turning the region pale blue.
Nine of the 11 starters in City's 2015 FA Youth Cup final team that lost to Chelsea were born in the city. Two-thirds of City academy players are now from the Manchester area.
“Ten years ago all our kids were in Manchester United or Liverpool shirts,” says Matt Wackett, who coaches the under-fives, sixes and sevens at Egerton Football Club in Cheshire, just south of Manchester's urban sprawl. “Now most of the kids are in Manchester City shirts.
“We can be quite cynical about these clubs and the way they are going about seeking talent. The emphasis is on casting the net far and wide, of bringing in as much talent as possible that will then be funnelled down as the years go on, whittled down to half a dozen kids.
City have recently invited Wackett to bring his under-fives in to their Etihad campus for a coaching session with their staff. That's 30 kids, of all abilities, some barely able to kick a ball.
“It's an example of winning the hearts and minds of parents as well as the kids,” says Wackett. “They have to invest in the parents, because ultimately they're the ones who have to take the kids there once or twice a week.
“City do that pretty regularly for clubs all around the north-west, invite groups in for a coached session, see the campus and its facilities.
“It's become a real aspirational thing – 'I want to be in a Manchester City shirt'. It's very attractive to the kids. If the same kids were asked if they'd like to go into United, some of them, in a childish manner, would have gone, 'Urgh, no, we don't want to go there…'”
It wasn't always this way. While City had the upper hand in the mid-1980s – think of the FA Youth Cup-winning side that contained Andy Hinchcliffe, Paul Lake, David White and the Brightwell brothers – the Ferguson-driven transformation of United's youth system, starting with the signing of a 14-year-old Ryan Giggs from City's ranks in 1987, saw United's hold on Manchester grow.
City still produced fine young players. Shaun Wright-Phillips, Stephen Ireland, Daniel Sturridge, Michael Johnson, Micah Richards and Nedum Onuoha all graduated from the youth ranks into the first team in the first decade of this century.
But it was a different model - an economic necessity to a club financially stricken and briefly in the third tier of English football, using facilities unrecognisable from the £200m Etihad campus that opened in east Manchester in 2014, with its 16 pitches, 7,000-seat reserve stadium, three gyms and hydrotherapy suite.
Then, young players trained at Platt Lane, a prosaic council-owned block in the somewhat edgy Moss Side. There were six members of staff, no security barriers and little control over who might turn up.
“We had to give priority to community groups,” remembers Jim Cassell, City's academy manager from 1998 to 2009. “Local students had the pitches on Wednesday afternoon. Our under-16s had to train from 9pm to 10pm.
“We had weddings, we had funerals. We had to be quiet so we didn't upset the mourners.
“Our pitches, because they were overused, were bumpy and bobbly. If you went on the wrong five-a-side you'd be playing with the taxi drivers. We had to leave rooms free for Weight-Watchers meetings.”
United had the locally born superstars – Paul Scholes, Nicky Butt, the Neville brothers – and the economic supremacy to entice the wannabees in generations below.
“United's secret was to allow the local scouting network to become a real stronghold,” says Derek Langley, head of recruitment at United for 16 years until 2016.
"Being a United man I didn’t want to lose any player to any other club. The scouts were indoctrinated with that ethos, and 99% of scouts were United fans too.
“It was a case of making sure the scouts did their job in the right manner. We didn't want to alienate people, we didn't want to anger parents. We had to forge relationships with as many clubs as possible, and show them that we did things the right way.”
Cassell agrees. “We knew all the United staff, they all knew us. We had great respect for each other and we loved to play each other.
“Obviously one year we'd have the better team and beat them and the next they'd give us a bit of a thrashing, but we both understood that we were doing the best we could to produce players for our own first teams.”
The change came with City's takeover in 2008 by Sheikh Mansour. First it was about the senior side – signing Robinho for £32m on the day that sale went through, then Pablo Zabaleta, Nigel de Jong and Vincent Kompany in the weeks that followed, three of the pivotal men in forming their Premier League-winning side of 2012. Soon it became about winning the future too.
“It was obvious that changes were afoot from an early stage,” says Langley.
“We knew there would be a huge challenge, and we tried to meet it head-on, but it's impossible to meet it head-on with the money they now have at the club.
“They had a big push from a scouting perspective. And you need the scouts on the ground, to have them physically there. You have all the analytics, but that information still has to come from somewhere.
And so the rivalry spread. Facilities built, money invested, Etihad campus transforming a long-neglected brownfield site in Clayton, just across Alan Turing Way from City's stadium, it became a battle for human resources: kids, coaches, scouts.
“When I was at the club we had an understanding that we wouldn't poach each other's staff,” says Langley, who also produced an impressive generation of players for Blackburn in the 1990s.
“I had a fantastic relationship with the teams at City, Liverpool, Everton. But things like that change. You can't stop it. You'll have a situation where someone thinks, 'they could do a good job....'
“I would love to be the one who says there isn't any poaching of kids, but we know things go on.
“The regulatory bodies need to follow up on these things, but they can be hard to prove. You have to think how that's going to affect that boy's lifestyle, his demeanour, his whole support mechanism. How does it change the losing club?
“It's a minefield at the moment.”
And what of those young talents captured by all this trawling, the kids who could be the future and yet could also find themselves the past before they are even halfway through primary school?
James McAtee is rated as one of the most exciting talents in English football, his switch from United to City at the age of 11 talked about by some at the Etihad as their own Giggs moment.
“The first to come calling were City,” says his father John, a former rugby league professional at St Helens. “They sent two coaches into his school, and they just had him in the playground, kicking the ball. One of them noticed he could play a little bit, and then they took him in to Platt Lane.
“He signed for United at nine, because his elder brother was also there, and with my work I couldn't take one to one place and one to the other. But things didn't work out for the older one, so I said it's best if the younger one doesn't stay here. So I moved him to City in his under-11 season.”
City had a pearl handed to them. McAtee, not 15 until later this year, has been compared to a young Jack Wilshere, a kid who can dribble, shoot, pass and run with natural head-up balance. And he is being made to work for it.
“He loves it, but it's tough,” says his father. "It's a long day. Every morning he's up early to get the train to St Bede's, at lunchtime they leave the school and go to City, train all day and then he gets the train home. It's 12- or 13-hour days, every day.
“It's hard. He's not the biggest of kids. But he's turning into a player. He's got better and better. It's absolutely brilliant, when you see them enjoying themselves, when he comes out of the dressing room and says, 'How did I do, Dad?'”
Then there is the other side to the tale, the story of the kids sucked in but spat out.
“My son was five at the time, playing quite well,” says one father, who spoke to BBC Sport on condition of anonymity.
“He'd played in a match, scored seven or eight goals, and after the game I was approached by a scout from City. He told me he was impressed by my son, and would like him to come in.
“I felt very, very proud. When someone comes up to you and says your son can go to City or United, initially you jump at it without any thought.
“And he struggled. He was overawed by it all, the big difference between training with his friends and at a development centre. There was a lot more pressure, even at that age. I noticed straight away.
“He was there for 12 weeks. As things progressed he shunned away from making contact in the games, and was half the player he was when he initially went. His game suffered. His confidence went.
“I knew the phone call was coming. We were told he would be released, and it was very difficult telling him what had happened. I remember him sitting on the stairs and crying for about an hour. He just wanted to sit out on his own.
“It knocked him massively. At that age it's a big hit to the system. It's taken him two years to get back where he was.”
And so we come to now, when the young sons of former United players Robin van Persie, Phil Neville and Darren Fletcher all train with City, when City's under-14s have beaten United's 9-0, when United won the Under-21 Premier League three times in four years, where City are the reigning champions of Under-18 Premier League.
All skirmishes in the cold war, all scalps claimed. But which side is winning? And what does winning even look like?
“I think the balance has gone City's way,” says Jim Cassell, on United's staff as a player before he ran City's academy.
“If you've won the title as many times as United, if you've won the European Cup, then City were playing catch-up, but without doubt they've taken advantage of their financial status.
“City have the dominance. We always regarded United as the leading club in England, let alone Manchester, but the ground that City have made up is terrific.”
Derek Langley, now in charge of recruitment at the agency OmniSports, is realistic about the allure of the club he served for so long.
“City have proved to everyone now that they have the competitive edge at this period of time,” he says. “They don't have the history, but the history can only survive for so long. The lads coming through now don’t realise what the Class of '92 was.
“United have to think really hard now how they can reinvent the competitiveness, and cope with all the other things – education, relocation, transportation – that needs to be rethought.”
The 9-0 derby win for City's Under-14s in November 2015 was no outlier. Three months ago the same group, now under-15s, beat their United counterparts by the same scoreline once again. In the same week City’s current Under-14s won their derby 6-0, and the Under-13s won theirs 5-0.
It is chastening stuff for Nicky Butt, a graduate of that Class of '92 brought back after the first thrashing to replace his former team-mate Brian McClair as head of United's academy.
But the real casualties of this arms race may be the kids themselves, whether an under-14 who finds his performance pored over in a national newspaper, or the five-year-old courted by both clubs only to be ditched before his ninth birthday, or even the rare prodigy who makes it through every exacting stage only to see a foreign star bought in his place when he reaches maturity.
It was always the case at Manchester United that the result is not the important thing in the early years of a boy's development," says Derek Langley.
“The manner of the defeat you could possibly look at, but you’re not there to take a team through together. That's almost impossible. You're trying to develop the individual, with the ultimate aim of getting that player to the first-team.
“I would far rather work on the things that require improvement in that boy. No-one likes a 9-0 thumping, but it’s what you learn from it that matters. And how you challenge them to make sure that next time they play City they play better.”
What does winning look like? It looks like more kids in the replica shirts of that club, more sucked in to the academies, more boasting to be done about teenage thrashings. It looks like kids from tough areas given private educations, young talent given world-class coaching, kids from muddy council pitches playing on facilities good enough for World Cup winners and superstars.
It can also look like fine youth sides stripped of their best talent, of school teams where the best kids are not allowed to play lest they tire themselves out before academy friendlies, of kids who were promised the best and yet came up short.
Dave Horrocks stands by the door to the Fletcher Moss changing rooms, back to the Mersey, face turned away from that fierce winter wind.
“Add in the opposition teams, and you could easily have three or four hundred kids playing out here on a Saturday morning,” he says. “And it looks fantastic, when you stand by the changing room doors looking out, all those kids enjoying themselves.
“We want to work with all the clubs. We want to give all our children the best chance. Some of our kids are Bury-standard or Rochdale-standard. We had nine signed by Stoke City last season.
“If City, with the billion-pound investment they have, ask you to come in and train with them, it's a lovely compliment to be asked to be part of that.
“If you trawl, you will get some big fish. But it's the distasteful way most of those kids will get released. It's like the X-Factor boot camps. You lot sit here, you're staying. You lot since over there, you're going. There's no letting people down gently.”
He sighs, and goes back inside, on a cold day, in a long cold war.