Frederick the Great is recorded to have said: "When Marshal Subise goes to war, he is followed by a hundred cooks, but when I take the field I am preceded by a hundred spies."
The present leader of the German army might well say the same, though probably his "hundred" would amount to thousands.
We hear of them dressed in plain clothes as peasants, and signalling with coloured lights, with puffs of smoke from chimneys, and by using the church clock hands as semaphores.
Very frequently a priest was arrested and found to be a spy disguised, and as such he was shot. Also a German chauffeur in a French uniform, who had for some time been driving French staff officers about, was found to be a spy, and so met his death.
Early in the present war the German field spies had their secret code of signs, so that by drawing sketches of cattle of different colours and sizes on gates, etc., they conveyed information to each other of the strength and direction of different bodies of hostile troops in the neighbourhood.
As a rule, these are residential spies, who have lived for months or years as small tradesmen, etc., in the towns and villages now included in the theatre of war. On the arrival of the German invaders they have chalked on their doors, "Not to be destroyed. Good people here," and have done it for some of their neighbours also in order to divert suspicion. In their capacity of naturalised inhabitants they are in position, of course, to gain valuable tactical information for the commanders of the troops. And their different ways of communicating it are more than ingenious.
In some cases both spies and commanders have maps ruled off in small squares. The watchful spy signals to his commander, "Enemy's cavalry halted behind wood in square E15," and very soon a salvo of shells visits this spot. A woman spy was caught signalling with an electric flash lamp. Two different men (one of them an old one-legged stonebreaker at the roadside) were caught with field telephones hidden on them with wire coiled round their bodies. Shepherds with lanterns went about on the downs at night dodging the lanterns about in various ways which did not seem altogether necessary for finding sheep. Wireless telegraphs were set up to look like supports to iron chimneys.
In the South African Campaign a Dutch stationmaster acted as field spy for the Boers for a short time. It was only a very short time. His town and station were captured by my force, and, in order to divert suspicion, he cut and pulled down the telegraph wires, all except one, which was left in working order. By this wire he sent to the Boer headquarters all the information he could get about our forces and plans. Unfortunately, we had a party of men tapping the wire, and were able to read all his messages, and to confront him with them shortly afterwards.
Another stationmaster, in our own territory, acted as spy to the enemy before the war began by employing enemies as gangers and platelayers along the line with a view to the destruction of bridges and culverts as soon as war was declared. There was also found in his office a code by which the different arms of the service were designated in terms of timber for secretly telegraphing information. Thus:
| Beams | meant | Brigades |
| Timbers | " | Batteries |
| Logs | " | Guns |
| Scantlings | " | Battalions |
| Joists | " | Squadrons |
| Planks | " | Companies |