Avatar Kyoshi kills the warlord Chin and separates Yokoya from the mainland, founding Kyoshi Island
Prior to the Hundred Year War, the city was an important center of commerce. However, it was destroyed by the Fire Nation during the first wave of attacks due to its strategic location and importance to the Earth Kingdom.
King Bumi single-handedly liberates the city of Omashu from Fire Nation occupation during the solar eclipse
Whaletail island was chosen as both a symbolic location near the Southern Air temple, where Avatar Aang is from and where the war began, and as a neutral, uninhabited and unclaimed island, for the peace accords following the Hundred Year War. Fireord Zuko of the Fire Nation, Avatar Aang of the Southern Air temple, Chief Hakoda representing the Southern tribes and Chief Arnook of the North, as well as Earth King Kuei and the council of Generals met here to finalize the ending of the war, and to move forward with reparations.
The Harmony Restoration Movement was a campaign to remove the Fire Nation presence in the Earth Kingdom by transferring the Fire Nation colonials back to the Fire Nation. It was proposed by Avatar Aang at Earth King Kuei's re-coronation ceremony and was greeted with cheers from the Earth Kingdom citizenry. However, the movement eventually led to a conflict between Earth King Kuei and Fire Lord Zuko, mediated by Avatar Aang. The Harmony Restoration Movement ended with the creation of a new joint government in the former Fire Nation colonies which eventually led to the creation of the United Republic of Nations.
More of a standoff than a proper battle, Yu Dao was the center of conflict regarding the fate of the Fire Nation colonies post-Hundred Year War. The Battle for yu Dao was a standoff between Fire Nation and Earth Kingdom forces over the fate of the colonies, now the home of a combination of Fire Nation and Earth Kingdom citizens of mixed heritage who did not want to be forced from their homes.