The Alliance of Altana is the name given to the collective forces of the Kingdom of San d'Oria, The Federation of Windurst, the Republic of Bastok, and the Grand Duchy of Jeuno, the latter being the regulating body, in Final Fantasy XI.
Before the events of Final Fantasy XI, a Crystal War ravaged Vana'diel. The Beastmen Horde, united under the Shadow Lord raged total war on Vana'diel. For the first months of the war each nation separately combated the Shadow Forces, to little avail. Facing imminent defeat the Kingdom of San d'Oria, the Federation of Windurst, the Republic of Bastok, and the Tavnazian Marquisate joined together under the regulation of the Grand Duchy of Jeuno, which had been politically neutral since its foundation. For the first time in Vana'diels' history, each nation stood united as one.
Eventually through the joint efforts the Alliance triumphed over the Beastmen hordes. However the victory came at a high price, along with death of thousands of allied troops, the city of Tavnazia suffered total destruction from an orcish bomb of unprecedented power. The blast was so powerful the peninsular on which the city was placed became detached from the mainland, resulting in the remaining nations being unable to mount a rescue effort. Everyone in Tavnazia is assumed to have perished.
After the Crystal War
With the war's end most nations were in ruins and a pooling of resources would be needed to quicken reconstruction. With this in mind the remaining nations upheld the alliance and its values. Trade routes and Airship services were opened up between nations, along with each city constructing embassies to represent other alliances members. The alliance partakes in a system known as Conquest for military training purposes and division of land ownership.