In most Total War games, logistics is entirely ignored. Factions can communicate and intercept messages going from anywhere to anywhere without problems, and they don't need to worry about getting armies or agents to the enemy territories, as that is hand-waved away.

Some Total War games don't go that route, and instead make logistics a part of their rules. The sections below represent some logistical rule variations that may be applied separately or together.

Military Logistics
In a game using military logistics, your army must actually have to have a route to the enemies territory in order to attack them. For instance, if Nation A wants to attack Nation B, but nation C is between them, then A will have to get C's permission to cross C's land in order to successfully attack. If C refuses, Nation A must either choose to attempt to fight their way through to B, or simply not engage in the offensive. This variant is generally use with a map that has concrete divisions of territory.

Espionage Logistics
In a game using Espionage Logistics, intercepting messages can only be done if it passes through your territory, a territory adjacent to yourself, or a territory where you have set up a spy network for that purpose. To determine if a message passes through your territory, draw a line from the center of the senders territory to the center of the receiver's territory. If it passes through one of the territories, you can intercept and you can read it should you have sufficient Espionage. If it does not pass through a territory satisfying these conditions, than you cannot read it, no matter your Espionage score.