In 1847, the Mexican-American war began after the U.S. annexed Texas. In the fighting that followed, a marines' song called "The Halls Of Montezuma" flourished. One hundred and seventy years later, Manchester United fans sing a terrace song to the tune, which goes:

From the banks of the River Irwell / To the shores of Sicily
We will fight, fight, fight for United / 'Till we win the Football League...

To hell with Liverpool / To hell with Man City (They're s---!)
We will fight, fight, fight for United / 'Till we win the Football League.

It will surely be sung in the bars of Houston by United fans ahead of the friendly, which is a marketing, commercially minded exercise. But friendly? Do you think Jose Mourinho or Pep Guardiola could stomach a 5-0 defeat?

The pressure is on both men after underwhelming league finishes last term. They were brought in to win titles, and managerial fuses aren't as long as they used to be, with near-instant success expected after significant expenditure. Neither would get the three-and-a-half years Sir Alex Ferguson got before winning a trophy.

Both have been England's biggest spenders in recent years, too. In 2013, City spent £72 million in the transfer window and United £27.5m on Marouane Fellaini. In 2014, City spent £53m, United $119m. Two summers ago, City splashed out £144m, United £113m.

The figures continued to rise. Last year, City paid £175m on new players, United £149m. In the transfer window so far, Guardiola's side have splashed out £144 million, United £106m. That's over one billion pounds in five summer transfer windows on new players. Meanwhile, three miles from Old Trafford, the under-10s of Trafford FC are scratching around for £170 to buy the bigger size-four footballs required for this season.

United and City are both good with their community and foundation work locally, but it's what happens on the pitch with the first team that matters most to fans. Mourinho, who remains very popular with United fans, is getting the squad he wants. But he wants more. He wanted four players this window but has downsized his expectations to three. He has continually put pressure on his boss Ed Woodward to do more in the transfer market, which isn't always appreciated, especially when his representatives brief against Woodward.

This is what you get with Mourinho, which United knew when they gave him the job. He's not compliant; he'll push and push because he wants the best. Woodward, who briefs himself, has to deal with it. So does Mourinho when things don't go ideally, because football seldom goes ideal. Mourinho knows that he can't keep burning bridges every two years at clubs and genuinely wants to spend more time at United than any other club that he has managed.

Their working relationship contrasts completely with the tight axis of power between Ferguson and his chief executive David Gill. The pair worked in tandem, with trust absolute as they took a devilish delight in keeping information from journalists before surprising them with transfers. Gill, probably the only man to tell Ferguson off, had little time for journalists while Woodward is more open, though he'll admit he was too open when he first took charge in 2013. A few journalists mistook the trust he put in them but contacted him so frequently that he regretted giving them his phone number.

Mourinho will continue to be asked about United's transfers every time he speaks to the media, though he's far more cautious about his responses than he was a year ago. It's also not in his interests to talk up the probability of transfer deals when they're not yet completed. Giving information away only plays into the hand of the selling club, but he's also respectful when talking about players who are contracted to other clubs.

Woodward is expected to stay in Europe as United continue to pursue Mourinho's targets: namely, a defensive midfielder and a winger to ping the ball into Romelu Lukaku. United may be richer than they've ever been, but it's harder for them to bring in the players they want since the rest also got richer and are as reluctant to sell their players as United would be to sell David De Gea.

Transfer targets will be relegated from interest when United and City meet in the stadium where Javier Hernandez made his debut for United in 2010 in front of an astonishing crowd of 70,728. Football is popular in Houston, home of the Dynamo, who were only founded in 2005 when they were part-owned by the retired boxer Oscar De La Hoya.

The city has a large Hispanic community, boasts its own smart soccer-specific stadium and average crowds of 18,000, with fans singing in Spanish and English. That will suit the United players, a sizable number of whom communicate in Spanish in the dressing room though it's always in English on the pitch.

United fans will heavily outnumber their City counterparts in Houston. There are fans of both clubs travelling from Manchester plus expats like pensioner Tom Clare, a Mancunian who has written books about the Busby Babes and who now resides in Houston. Along with former United goalkeeper Gary Bailey, himself a U.S. resident, Tom will host a pre-match party for United fans.

It wouldn't trouble Tom if he didn't see a single City fan, while officials from both clubs who may be neighbours in Manchester will keep a distance from each other while together on the other side of the world.