I couldn’t find the answer anywhere but, I recall in ancient times (possibly Nordic or Roman) one army lit its fires for the night and pretended to be still there but in reality left within the cover of the night(outside the enemies walls I think too). I believe the invasion came at a high cost originally? Sorry if this is too vague or has happened before but I know it was a very large movement with hundreds of troops leaving in the night.
This might be during the Wars of the Diadochi (Hellenistic age), at the Battle of Gabiene (315 BC), between the two Alexander the Great's succesors, Antigonus and Eumenes. Here's one quote:
"To fool Antigonus, Eumenes constructed a camp that from a distance looked large enough to hold his whole army, and he ordered the men he had with him to light enough fires to make it appear that all his soldiers were present. The ruse worked; Antigonus believed that his manuever had failed to surprise his enemy and that further forced marches would not be beneficial; instead, he stopped and rested his men, allowing Eumenes enough time to bring up his entire army from their various winter quarters."
Stefan G. Chrissanthos, Warfare in the Ancient World: From the Bronze Age to the Fall of Rome, p. 94.