What is "back post"

Usage examples of "back post".

Major McColloch, who had been warned by Wetzel of the fever of unrest among the Indians--a fever which broke out every spring--had gone to Fort Pitt with the hope of bringing back reinforcements, but, excepting the young soldier, who had volunteered to return with him, no help could he enlist, so he journeyed back post-haste to Fort Henry.

It's the sort of idea that would appeal to some Metro-Dade commissioners, who seem primed to cave in to industry pressure and roll back post-Andrew reforms.