Read this paragraph from the dark game.

to assure that the intelligence reached the commanders as quickly as possible—the postal services having become slow and unreliable—van lew created a system of couriers that moved the intelligence on its way without burdening one operative with the responsibility (and danger) of making the entire trip. she also created a credible cover story for each of her couriers, should they be stopped and questioned along the way.

the central idea of this paragraph is that

the postal service at the time was slow and unreliable.
secret intelligence needed to reach the commanders quickly.
van lew used multiple messengers to get her information across.
van lew gave all her couriers a believable cover story to hide their mission.