Earthbender rebellions

The Earth Kingdom Rebellions were an armed uprising against the Fire Nation, formed during the later stages of The War at an unknown time after the Coup of Ba Sing Se in 100 ASC. Its success surprised and alarmed the Fire Nation. It was admitted by a Fire Nation General that the powerful Fire Nation armies in the Earth Kingdom were insufficient to put down the threat, and that Fire Nation domestic forces were required for reinforcement.

The uprisings and its successes were mentioned to Fire Lord Ozai in a war meeting a day before the eclipse. Acting upon this information, Ozai decided to use the power of Sozin's Comet to burn down the Earth Kingdom, ending the rebellion once and for all. . The plan proved to be a failure, with Ozai's defeat in the Battle at Wulong Forest.

Now that the war is over, it can be assumed these rebellions have ceased.

Liberation of Omashu
On the Day of Black Sun, King Bumi successfully broke free of his metal chamber. Taking advantage of the soldiers' loss of Firebending, Bumi used his exemplary Earthbending abilities to defeat all of the powerless guards and soldiers trying to stop him. With the guards out of the way, Bumi begins to save his city.

With extremely powerful Earthbending moves, Bumi cast out every Fire Nation-constructed building. To signify Omashu's liberation, Bumi destroys the statue of Fire Lord Ozai, first by placing a smiley face on it, before causing it to crash right into the governor's house and destroying the metal bridge connecting to the city immediately after the guards fled.

Bumi celebrates his victory by enjoying a delicious piece of rock candy.

The liberation of Omashu was a disaster for the Fire Nation, and proved to be the beginning of the Earth Kingdom's ultimate liberation from the Fire Nation Armies.

Liberation of Other Minor Towns
Bumi's liberation of Omashu began what would be the liberation of many small Earth Kingdom towns, creating a big problem for the Fire Nation. Among the various towns that were liberated was the Mining Village. Under the leadership of Tyro and his son Haru, that village's population was successful in reclaiming their town after years of enslavement and persecution. (Although this would have happened prior to the Liberation of Omashu, as both Tyro and Haru participated in the Invasion of the Fire Nation on the Day of Black Sun.)