[Grammar] captured by the Germans in a retreat

[jacob123]

Does "in a retreat" refer to the retreat of the British forces or does it refer to the retreat of the German forces?

In July last I had a sitting with Mr. J. J. Vango, in the course of which the control suddenly told me that there was standing by me a young soldier who was most anxious that I should take a message to his mother and sister who live in this town. I replied that I did not know any soldier near to me who had passed over. However, the lad would not be put off, and as my own friends seemed to stand aside to enable him to speak, I promised to endeavour to carry out his wishes. At once came an exact description which enabled me instantly to recognize in this soldier lad the son of an acquaintance of my family. He told me certain things by which I was made doubly certain that it was he and no other, and he then gave me his message of comfort and assurance to his mother and sister (his father had died when he was a baby), who, for over two years, had been uncertain as to his fate, as he had been posted as "missing." He described how he had been badly wounded and captured by the Germans in a retreat, and that he had died about a week afterwards, and he implored me to tell his dear ones that he was often with them, and that the only bar to his complete happiness was the witnessing of his mother's great grief and his inability to make himself known.

"The History of Spiritualism," by Sir Arthur Conan Doyle

 

[probus]

The passage is not explicitly clear, but surely only a retreat by British forces makes sense. It is implausible that German troops who were in the process of retreating would attempt to capture an enemy soldier.