In the late 1960s and early 1970s, millions of young Chinese were transported to the countryside to 'undergo re-education by the poor peasants'. Separated from their families and deprived of their adolescence, they became known as the 'sent-down youth'. Kathrin Hille attends a poignant reunion. Portraits by Bakas Algirdas

Ma Shangzhu's face lit up with a radiant smile as she leaned out of the train window and waved goodbye to her father. In a white blouse and plain cotton jacket with a plaque of Chairman Mao on her chest and two braids behind her ears, the 18-year-old from Shanghai looked expectantly into the distance. Today it is difficult to recognise the young woman with the eager smile in the wax-white, wrinkled face bent over that photograph from 45 years ago. “It was not like this,” says Ma, a petite woman who appears older than her 63 years. “You can't tell from this picture what I felt that day.”

On September 17 1968, the train took Ma and 305 other students more than 2,000km from her middle school in Shanghai, to the wooded hills and deserted plains of China's far northeast, close to the Russian border. They were among more than 17 million Chinese urban youths sent to the countryside to do hard labour on farms and in forests in the 1960s and 1970s.