A bivouac, according to the Oxford English Dictionary, is “a temporary encampment of troops in the field with only the accidental shelter of the place, without tents, etc.” Or as the Field Service Pocket-Book put it more succinctly, “an encampment without tents or huts.”(1)
Setting up a bivouac was part of the training of the 55th Battery. They seem to have had good weather for it, so they did not suffer from the lack of tents or huts. Perhaps it all seemed a lark. In fact, it looks a bit like a picnic, in the company of horses.
(1) Field Service Pocket Book. HMSO, 1914, viii.
The photograph is from Percy’s small album.