The Battle of Dantooine occurred during the Imperial Period when an Imperial strike force attempted to find and kill Falon Grey, who was hiding on the planet. The clone X1 spearheaded the assault, but X2 joined the rebels inside, taking a different path from his brother.
The Dark Lord of the Sith Darth Vader sent X1, X2, and other troops to Dantooine to root out and destroy a Jedi that the local villagers had been harboring onplanet. While en route to Dantooine, X2 decided that siding with the Galactic Empire was wrong, and opposed the Empire, as well as his clone brother, X1.
X2 then arrived on the planet, defected, and helped the villagers repel the brutal Imperial invasion. During the battle, he encountered the Jedi Falon Grey, a veteran of the Clone Wars. Grey was revealed to be his and X1's genetic father.
X2 meets Falon Grey.
With the initial Imperial invasion in full swing, clone stormtroopers were sent to villages known to harbor Rebel activists, and assaulted the locales using AT-RTs.
X2 managed to halt the charge by using mines to cut off a reinforcement point at a landing pad, but this action did not forestall the expedition for long. Imperial LAAT gunships were en route, with reinforcements for the Empire in transit. It fell to X2 to man the village's AA gun and shoot down the marauding transports.
Towards the end of the battle, Grey, X2 and a group of Dantooinian rebels escaped through the Jedi Enclave on the planet, planning to make use of a primitive hangar to escape. When the hangar door was finally opened with help from X2, several Imperial LAATs carrying X1 and a group of clone soldiers appeared to block off their escape. They mercilessly opened fire, killing the rebels and wounding X2.
Grey incapacitated the clones, as X1 engaged him with a force pike. Grey defeated him, surrendered the force pike to X1 and yielded his lightsaber as a gesture of reconciliation. X1 disabled Falon Grey with the force pike, and dispatched him with a blaster shot. X1 and the other soldiers left, leaving the unconscious X2 for dead.
Grey healed X2 before finally dying.
The Invasion of Dantooine was created for the 2009 video game Star Wars Battlefront: Elite Squadron, and is a playable level in all versions of the game. The mission serves to establish backstory for X1 and X2, and how they came to oppose each other.