This Great War period guide to the art of flag semaphore was original
published by Gale & Polden and formed part of their respected "Military
Series". Each letter of the alphabet is illustrated with a front facing
soldier using this rapid means of field communication. Semaphore could
usefully be employed at short distances, as between columns and their
advanced guard, or rear guards, across rivers, or fire swept zones, and
to connect an attacking line with its supports.
Flag semaphore is the telegraphy system conveying information at a
distance by means of visual signals with hand-held flags. Information is
encoded by the position of the flags; it is read when the flag is in a
fixed position. Semaphores were adopted and widely used in the 19th
century.