With the same determination that allowed them to transform desolate land into productive fields, the returnees have organised a weekly protest for the past three years to seek higher benefits from the Shanghai government.

Recent revelations that corrupt Shanghai officials were stealing from the city's pension fund have increased their anger. The scandal has already ousted Shanghai's top leader, party secretary Chen Liangyu .

'We ought to receive the same treatment as Shanghai workers,' one returnee said. 'The government must take responsibility for its past mistakes and give us compensation.'

An estimated 100,000 Shanghai 'educated youth', their ages ranging from below 16 to the mid-20s, went to Xinjiang from 1963. The decision to send them was reportedly made by Wang Zhen , then a vice-premier who eventually rose to vice-president.

Shanghai was, as usual, the vanguard of the revolution. The practice of sending students and urban youth to rural areas would later grow into a political campaign known as 'Up to the Mountains and Down to the Countryside' during the 1966-1976 Cultural Revolution.

'It is imperative that educated youth go to rural areas to be re-educated by the poor and lower-middle peasants. We must convince cadres and other people in cities to send their children ... to the countryside,' Mao Zedong wrote in a People's Daily article headlined 'We Have Two Hands Too. We Will Not Loaf Around in the City'.

Although many in Shanghai volunteered, some had little choice, and others were coerced. Neighbourhood officials allowed families to keep their other children in Shanghai if they would surrender one for Xinjiang.

Many of the families who sent children had bad class backgrounds from working for foreign companies before 1949 or being labelled 'rightists' in earlier political campaigns. The government blocked their children from attending university or finding good jobs.

The send-offs from Shanghai were grand events. Dressed in army uniforms with Mao buttons pinned to their chests, members of the children's crusade excitedly boarded trains hauling bundles filled with food and supplies packed by worried mothers.

Arriving in Xinjiang after a week-long journey by train and truck, their idealism was quickly eroded by the rugged conditions. The soil they tilled was often barren or alkaline. Temperatures ranged from minus 20 degrees Celsius in winter to more than 40 degrees in summer.

Mr Wang and his group of nearly 200 went to an area outside Aksu city, along the old Silk Road trading route. They ate boiled turnips and slept in pits covered with tree branches and dirt. 'If you were walking at night and weren't careful, you would go through someone's roof,' he said.

This was life in the Xinjiang Production and Construction Corps, a military-linked conglomerate engaged in agriculture and industry. Popularly known as the bingtuan (soldier group), the corps encouraged migration and protected stability in the border region.

Still in existence today, it is a 'state within a state', operating a system of labour camps that have drawn criticism from human rights groups.

The Shanghai contingent remained out west for years. Some escaped by sneaking back to Shanghai, fleeing to other provinces. Many died. Young women could find a way out by marrying local husbands.

Only after the Cultural Revolution and the beginning of reforms in 1978 did those sent to the countryside regain hope about the prospect of going home.

As Shanghai people sent to other parts of the country began to trickle back to the city, those in Xinjiang found their return blocked by a set of rules known by its number, Document No 91, which said the government should take steps to ensure that they stayed put.

'Take practical, feasible measures to resolutely make the vast majority of Shanghai youth remain stably in Xinjiang,' ordered the document, issued by Shanghai and Xinjiang with the backing of the central government.

For Shanghai's part, this meant tactics such as detaining returnees, shutting down their small businesses and barring their children from attending local schools. This went on through the 1980s.

Various theories have circulated about why Shanghai specifically discriminated against returnees from Xinjiang, including their poor political backgrounds and the city's reluctance to accept a mass influx of people who were still needed in the western region.

In the 1990s, however, looser controls and retirement have allowed an estimated 20,000 to return to Shanghai.

Their return has highlighted a major flaw of the mainland's pension system: lack of a national scheme. Residents across the country contribute different amounts and receive different benefits, and localities manage the funds without central government oversight.

Some of the Xinjiang returnees never paid into a retirement scheme because they were working before pension reforms started. Others paid into a fund, but were unable to transfer their accounts to Shanghai.

Those who are receiving benefits from the Shanghai government have found that the levels are far below those of the city's other retired workers, since they are based on Xinjiang salaries and living standards. Mr Wang, 60, receives about 500 yuan a month - roughly half the average Shanghai level. His medical insurance adds a further 20 yuan. He relies on his children and renting his home to a retail shop to supplement his income.

He bristles at the idea of accepting poverty relief, saying he believes it denigrates his contribution to the nation. 'Our slogan is that we want the same treatment given to Shanghai's retired workers,' he said.

No one will openly say who organised the weekly protests, which began in June 2003. Shanghai has handled the demonstrations delicately, since the protesters are elderly and considered patriots by many. Still, authorities view the returnees as a threat to state security and make periodic arrests.

After foreign journalists stumbled on the protests in March 2004, authorities used it as an excuse to crack down. Police held reporters from the South China Morning Post and French news agency Agence France-Presse for several hours.

The following week, the city sent hundreds of riot police to clear the protest and later offered a one-off increase of 50 yuan in benefits as part of the government's dual approach to the problem. Police have since warned foreign journalists about covering the demonstrations and protesters have been cautioned about speaking to reporters. A leader of the group recently declined to be interviewed, saying: 'We can handle our own internal affairs.'

The protests, now held every Wednesday outside an office of the Shanghai Labour and Social Security Bureau on Hankou Road, still attract hundreds. They even play a social function, allowing retirees with shared experiences to meet and exchange information.

In the two months since the Shanghai pension scandal came to light, talk has turned to whether reforms to help their plight could follow.

Zhong Renyao , a professor at the Shanghai University of Finance and Economics who advises the government on pension reform, said the corruption case could bring change. He is calling for a move towards a unified national system and more transparency on the part of local governments over how the funds are invested.

Ideally, the central government would take control of local pensions, but some provincial and city level officials would oppose such a move, the professor said. As a halfway measure, the central government could set uniform rates for pension contributions and benefits. 'This is entirely possible,' he said.

In the meantime, the Xinjiang returnees cling to the hope that they might one day receive better treatment. Lawyers have refused to take on their case, so they have launched a letter-writing campaign to ask the Supreme People's Court to accept a lawsuit.

'If we want to eat, we have no money to see a doctor. If we see a doctor, we have no money to eat,' one letter said. The court hasn't responded.

Xia Lin , who spent more than 30 years near Korla city farming and doing menial labour before returning to Shanghai in 1996, said he hoped the group's contributions to the nation would be recognised.

He wants someone to write the complete history of Shanghai youth sent to Xinjiang, but the topic is still too sensitive. One returnee, Xie Mingan , has written a trilogy, Bitter Love, about his personal experiences. The work had a limited printing. Overseas, stories of young people who were 'sent down' to the countryside are reflected in works such as the memoir Spider Eaters by Rae Yang and a movie directed by Joan Chen, Tian Yu, about a teenage girl who compromises herself in an attempt to return home.

Mr Xia, who is self-taught with only a middle school education, is the scribe of the group. He spends his days writing articles about their plight and letters to various government bodies.

He doesn't feel up to the task of writing a history, but he says the work should gather the collective experiences of the returnees. 'This is a history of the government using forced labour,' he said.

Some names have been changed