Stratton and Bates were prisoners of the Cybermen in the 27th century who had been partially converted into Cybermen, their limbs replaced by mechanical equivalents. Since full conversion had failed, they were put to work on the surface of Telos.
They escaped and tried to reach Cyber-Control to destroy the Cyber Controller, meeting up with Lytton and Griffiths along the way, but Lytton was recaptured and Stratton was killed when he tired to open the door to the time machine. Griffiths and Bates were killed soon afterwards by the Cybermen. (TV: Attack of the Cybermen)
Behind the scenes
In the Attack of the Cybermen novelisation, Stratton is given the first name of Lintus and is said to hold the rank of Flight Leader. They are both said to come from the planet Hatre Sedtry in the star system known as Repton's Cluster.