Large Transport Ship

Summary
The Large Transport Ship is an advanced ship type introduced by the Eagle King DLC, available to all faction groups. It is a very slow ship without a capacity for melee combat, but it can carry 2 brigades while most warships can carry just 1, and is much sturdier than basic Small Transport Ships."Giant double-hulled ship used for moving large units. These are much tougher and faster than small transports and can defend against warships, but can't attack."

- In-game Description

History
Double-hulled polyremes such as how the large transport ship is depicted in-game are speculated to have existed in some of the largest ancient navies, and may have been used as prestige vessels, being too unwieldy for use in battle.

One famous example of a ship suspected to have been double-hulled is the tessarakonteres, a massive ship constructed in Egypt in the 3rd Century BC with 40 files of oarsmen on each side of the ship and no less than 4000 oarsmen in total.

Tactics
Large Transport Ships are considerably more expensive and slightly slower than Small Transport Ships, while also not being available until much later in the game and carrying the same amount of troops and food.

However, they have significantly stronger defenses, giving them a much better fighting chance if the player is unable to prevent enemy ships from ramming them and engaging them in melee. As such, large transport ships offer much better security for the troops it transports, and can be a wise investment if the player is planning to move a naval invasion force through contested waters.