Seminal work on the nature, principles and practice of the art of reconnaissance, which even despite the aircraft and satellites of today's age remains an important task for military units worldwide. This edition includes Henderson's chapter of aircraft reconnaissance which was only just being tested on the Western Front in 1914 when he published the second edition of this book."e;THIS work is intended (and hence its pretentious title) to present a view of the subject of reconnaissance as a whole in the hope of assisting those whose duty or ambition it may be to prepare themselves to undertake the pursuit of information in war. There are two points which may seem to call for some explanation. If anyone should remark on the incompleteness of the work, and should complain that in discussing the details of reconnaissance. I have left a great deal unsaid, I would reply that I have endeavoured to consider only those details which seem to contain the germ of some principle of more or less general application. If, on the other hand, exception should be taken to the temerity of a foot-soldier in surveying; and perhaps overstepping the debatable ground which lies between the provinces of reconnaissance and cavalry tactics, my defence is that I went in search of knowledge and that such a quest is a reasonable excuse for trespass."e;