Teleporting

[Enkidoh]

-The Autumn War between Gridania and Ala Mihgo, which brought us the Grand Companies, chocobo barding, and the adventuring profession (to give out of work soldiers something honest to do).

Uh, please correct me if I'm wrong, but it was my understanding that the Age of Adventuring began following the Battle of Silvertear Skies (due to the build up of mercenaries that arrived in preparation for a Garlean invasion of Eorzea proper that never eventuated, and hence the Adventurer's Guild was then formed to supply employment for these now unemployed and heavily armed men and women).

The original game's manual states this and the official website used to as well, as shown:

The Age of Adventure
The guardian gods and goddesses known as the Twelve watch over the city-states of Eorzea. These tiny nations carved out a history of blood and betrayal, forging and breaking alliances as each warred over territory and sought to impose uncompromising interpretations of their patron deities' will.

The fate of the land would, however, soon change. Not fifteen years past, a new threat appeared from the east-the might Garlean Empire. With its fleets of behemoth airships and warriors brandishing weapons that spewed streams of fire, it crushed Ala Mhigo, the most powerful of the six Eorzean city-states. Galvanized by fear of a common foe, the remaining nations joined in a clandestine alliance. Fortunately, the dreaded invasion never came and an uneasy peace prevailed. Thus it was that Eorzea slipped into the "Age of Calm".

As the city-states continued to develop regular standing armies, a growing number of mercenaries and hedge knights found themselves without employment. Concerned at the rise in number of armed men and women resorting to acts of villainy to survive, several respected leaders gathered together to form a network of guilds. The guilds provided these lost souls with the chance to utilise their talents for the benefit of themselves and others.

Through the foresight and resolve of these leaders a new industry had emerged-and the era of adventuring had begun.

I know the Autumn War did involve the other citystates allying with Gridania though, but from what I was aware (based on the above info and other sources) the title and status of 'adventurer' didn't exist in the way we now know them at that point in time.