The Galleon is a fast and powerful military main battle ship that is capable of training infantry and cavalry directly onto foreign soil, acting as a mobile Barracks and Stables. Note that it will be unable to fire with its cannons during this process. They are significantly more resilient than the Caravel due to increased health and resistance. They may not have as high a DPS output as Caravels, but they still perform sufficiently as an attack vessel.
Most civilizations will find the Galleon capable of surviving battles in the early ages, especially when compared to a Caravel and make good tanks in the frontline while the latter exploit their higher damage. However Spanish Galleons (with cards) make excellent attack vessels and damage sponges in any age.
The Spanish have the strongest Galleons in the game if they take advantage of their cards. If they choose to do so the Spanish galleon has more hit points than any other ship sailing the seas in Age of Empires III and The WarChiefs, except the Spanish Frigate which has only 525 more.
With the release of The Asian Dynasties expansion, the Spanish Fuchuan becomes the highest hit point vessel in the game (25 more hit points than the Spanish Frigate) when received via the "TEAM 1 Fuchuan" card sent by a Chinese ally. Spanish Galleons can easily hold their own against the more expensive Frigates, Tekkousen, and Fuchuan or outrun them if necessary.
While extremely durable, the Spanish Galleon is slower than a Tlaloc Canoe and can't retreat effectively from combat with them. It also lacks the range of many other ships, this can be exploited by an opponent as a means of overcoming the durability and shoreline attack power. Particularly dangerous are the Fuchuan (with "European Cannons"), Tlaloc Canoes (with Water Ceremony and "Offshore Support"), Canoe (with Water Ceremony, "Offshore Support", or Fire Ceremony) and Monitors or Ironclads due to their long-range shots. When attacking enemy shores with the ship, Culverins can be dangerous to the Galleon. Augmented Fire Ships (with Home City Cards, etc.) can also be dangerous in large groups.
Blocking Galleon training
Walling up the shore so that there is no free space will prevent Galleons from training units onto the shore, as well as preventing any ships from being able to land troops. Even if a 1-2 area gap is left somewhere along the walled up coast (between the shore and wall), only 1-2 units will be landed or trained; units will not appear behind the enemy wall.
The Galleon must be close to the shore to train the units, and will also be unable to move and attack while doing so.
These square-rigged, three-masted warships were used primarily by European powers in the fifteenth through eighteenth centuries. Well-suited for carrying cargo and for war, galleons made up the bulk of the famous Spanish Treasure Fleet that carried plunder from the Americas back to Spain's waiting coffers. They carried around 30 cannon, fired from two decks in broadsides. Adaptations to the basic galleon design yielded heavy Spanish Galleons and the lighter, more maneuverable galleons of the British and other European nations. They were eventually replaced as multipurpose ships by the clipper, a fast cargo ship, and the massive Man-of-War.