Talbot Mundy 
The Hundred Days [EPUB ebook] 

Probably the spies deliberately provided false information about the raid in this quarter to ensure the passage of large squads elsewhere. Or the tribes learned to hide from aviation, which is not very difficult among those breeds and gorges, or even in open terrain, where the high grass at a distance resembled the waves of the sea with wind currents. Another probability lies in the rear. Raids from this Northwest border were so frequent for a thousand years that the invasion was no less probable than the desert rain.