* Iron discipline at a young age
* Sisi gave little away before making move
* Western diplomats fear he will fail
* Described as pious by those who know him (Adds military council approving presidential bid)
By Michael Georgy
CAIRO, Jan 27 (Reuters) - Three years after the "Arab Spring" toppled Hosni Mubarak, a secretive field marshal with a cult-like following is expected to announce his candidacy for the presidency of Egypt ahead of elections which he is expected to win easily.
Abdel Fattah al-Sisi, 59, has been urged to run by members of the public who reject the Islamist government he toppled last year, and by members of the armed forces who want a president who can face down growing political violence.
On Monday, Egypt's top military council gave him the green light to seek the presidency, and the interim president Sisi installed six months ago promoted him to field marshal from general.
Sisi has calculated that he can win the support even of some of those who backed Mohamed Mursi for president in 2012, who sought change from the era of former air force commander Mubarak, ousted in the revolutions that swept the Arab world.
But despite his present popularity, Sisi has no record as a democrat and has shown himself willing to use deadly force against those who disagree with him.
Sisi has trodden a careful path to power since overthrowing Mursi, Egypt's first freely elected president, last July.
It's the kind of measured advance he has made all his life, from his childhood in the dirt lanes of Cairo's Gamaliya district, to the highest rank in one of the largest armies in the Middle East. On Monday, the presidency announced he was promoted to field marshal from general.
Friends and family speak of him of as a man of few words and decisive action.
"He loved to listen and carefully study what was said. After he heard many opinions then he would suddenly strike," said his cousin Fathi al-Sisi, who runs a shop selling handicrafts.
"Abdel Fattah had one thing in mind: work, the military, rising to the top."
The world knew little of Sisi before he appeared on television on July 3 and announced the removal of Mursi after mass protests against the Islamist leader.
It was Mursi who appointed Sisi army chief of staff and defence minister in August 2012, perhaps his gravest mistake.
Mursi, a Muslim Brotherhood leader, wanted a young general to reduce the influence of the military old guard who had served under the autocratic Mubarak before the 2011 revolution.
His reputation for being a pious Muslim may have also appealed to Mursi.
But while Mursi appeared deaf to criticism, Sisi was tuned in to the rising discontent on the streets over the Brotherhood's mismanagement. Eventually he issued an ultimatum to the man who appointed him: Bow to the demands of protesters within 48 hours or the military would act.
Sisi, born on Nov. 19, 1954, honed his strategic skills in the shadowy world of military intelligence, which he headed under Mubarak. He was the youngest member of the military council which ruled Egypt for 18 months after Mubarak's fall.
Western diplomats say Sisi has been weighing whether to stand for president with his usual caution, and only decided to run recently.
"I suppose in the back of his mind is the fact that once he takes off his military uniform he suddenly becomes more vulnerable. There is always the chance of another takeover," said a Western diplomat.
A senior European diplomat says it's mission impossible.
"There is a belief among diplomats that he is making a big mistake by going for this job. He will expose himself and the army. The army may act if things go wrong and its image is tarnished. His fall could be sudden and sharp," said the diplomat.
Others also seem to have had their doubts. The prime minister of the United Arab Emirates, a major financial backer of Egypt after the downfall of Mursi, said it would be better if Sisi stayed in the military, before rapidly issuing a clarification saying that was not what he had meant.
Sisi's comments in the spring of 2013, when frustrations with Mursi were growing, suggested he would never stage a military takeover, let alone run for president even though he was deeply suspicious of the Muslim Brotherhood.
"With all respect for those who say to the army: 'go into the street', if this happened, we won't be able to speak of Egypt moving forward for 30 or 40 years," Sisi said then.
His own writings from his time at the U.S. Army War College in Pennsylvania in 2006 reflected an awareness that ensuring democracy in the Middle East may be fraught with difficulties.
Despite the risks, Sisi decided to run because pressure from the street had grown immensely and junior officers in the army urged him to contest elections because they did not feel politicians could handle Egypt's security challenges.
Islamist militants in the Sinai have stepped up attacks since Sisi ousted Mursi, killing hundreds of members of the security forces. And the Islamist insurgency is also gathering pace in other parts of Egypt, including Cairo.
Sisi enjoys the backing of the army, Egypt's most powerful institution, the Interior Ministry, many liberal politicians and Mubarak era officials and businessmen who have made a comeback since Mursi's demise.
Judging by his popularity, those forces are likely to give him plenty of time to prove himself as president, and there are no other politicians who could challenge Sisi anytime soon.
It remains to be seen whether Sisi's caution, which worked for him as a military strongman, can be translated into the skills needed as a president.
But his manoeuvring before Mursi's fall suggests Sisi could grow into the role of politician. He gained consensus among key players, from political leaders to clerics, before making his move.
Sisi has not said how he intends to tackle Egypt's many problems, from a stuttering economy to street chaos and escalating violence by militants. But those who have met him recently say he understands the need to fight poverty.
To many Egyptians, he seems invincible for now, a strong figure many are craving after years of turbulence.
At a coffee shop near his old neighbourhood, a Sisi poster is displayed alongside black and white photographs of previous soldiers turned rulers: Gamal Abdel Nasser and Anwar Sadat.
CAN HE SAVE EGYPT?
Admirers of Sisi, who knew him as a young man, believe his single-mindedness will be enough to rescue Egypt.
A resident who knew him said that while other local boys played football or smoked, Sisi and friends lifted barbells made of metal pipes and rocks - an early sign of the discipline that would take him far.
"Abdel Fattah always seemed to have a goal. He had willpower," said Aaatif al Zaabalawi, a dye factory worker who used to see Sisi in the area.
Neighbours say he came from a tightly knit religious family. His cousin said Sisi had memorised the Koran and his favourite dish was one often eaten on religious occasions.
The father encouraged him to work in his shop every day after school. He lived in a small apartment on the rooftop of a run-down building owned by his extended family.
"When an apartment was sold it was only sold within the family. Between brothers for instance," said his cousin, adding that Sisi had married within the extended family.
These days it's hard to escape Sisi. His image is on everything from mugs and t-shirts to pyjamas and even chocolates.
But critics, both Islamists and liberals, are alarmed by what appears to be a systematic stifling of dissent. Since Sisi removed Mursi, hundreds of Islamist protesters have been killed and thousands jailed.
In a few days in August, security forces smashed up Muslim Brotherhood protest camps in Cairo, killing hundreds in the bloodiest civil unrest in Egypt's modern history.
In recent months, the ruthless crackdown has extended to prominent liberals, including some who supported the army's removal of Mursi. Under Sisi, protesting without permission has become a crime which can be punished by a life sentence.
Sisi's election would signal a return to the oppression of the past, opponents say.
"It will be the final confirmation that Egypt is going backwards and that a corrupt, brutal, anti-democratic illegitimate leadership has aborted Egyptians' dreams of a democratic civil state," said Salma Ali, a spokeswoman for an Islamist alliance that opposes Mursi's removal.
Yet even visiting American politicians seem to have been swept up in Sisi mania. After meeting with Sisi, Representative Cynthia Loomis sounded deeply impressed.
"He spoke both aspirationally and as an implementer. It seemed like he was multi-dimensional."
Retired general Sameh Seif Elyazal says Sisi will likely ask Egyptians, who have driven out two presidents in the past three years, to be patient.
"He hasn't got an immediate solution for everything. I think he will tell the people we have issues and these issues will take some time. You have to bear with me. We will suffer a little bit," said Elyazal, who meets Sisi on a monthly basis.
But some wonder if the people will be more patient with Sisi than they were with Mursi, who lasted only a year in office. (Additional reporting by Tom Perry and Sameh Bardissi; Editing by Giles Elgood)