With Alderaan's naval defenses far from their charge, the forces of the Empire invaded the world in a swift and savage assault. Prior to landing their vessels, the Empire initiated a heavy orbital bombardment of the world, which decimated a number of townships and filled much of the atmosphere with ash and thick black smoke. Darth Malgus himself led the incursion force, which consisted of several thousand assault droids, hundreds of fellow Sith, large numbers of Imperial soldiers, and a bounty hunter. The ground forces were joined by vessels of the Imperial Navy, including starfighters and battlecruisers. Once his forces were on the planet, Malgus began a devastating campaign across the once-tranquil world. The Sith forces obliterated the local Alderaanian defense forces and continued on to burn entire cities to the ground. Jedi Knight Aryn Leneer participated in the conflicts on the planet, alongside Knight Satele Shan and other Jedi defenders. During the assault, the Imperials captured Alderaan's royal family, holding them hostage for a period of time and earning the ire of the Alderaanian government.
Commander Jace Malcom of Havoc Squad led his forces into position on a ridge overlooking the forest route that was to be traversed by Malgus's troops. As the Imperials marched past the Republic's position, the trooper commander opened fire with a blaster cannon, initiating the ambush. The rest of Havoc Squad leaped down from the ridge to join their commander in battle against the Sith through the forests of Alderaan. The troopers were able to destroy a number of assault droids with thermal detonators and blaster fire, but were eventually engaged by Darth Malgus himself. Upon seeing the Sith Lord impale one of his comrades, the commander took aim at Malgus, though his first several shots were ineffective. The trooper's final cannon blast engulfed the enemy commander in flames, badly damaging his face. When Malcom attempted to rush the Sith Lord and finish him off, Malgus assaulted him with Force lightning and threw him across the battlefield.
The remaining Sith forces gained the upper-hand in the skirmish, eventually forcing the Republic soldiers on the defensive. Havoc Squad troopers that fell behind were systematically executed by the Sith, until intervention from Satele Shan.  The Jedi Knight allowed Havoc Squad the opportunity to press their attack once more while she engaged Sith Warriors, their war droids, and Malgus himself. Shan and the Sith Lord's fierce melee was nearly ended when Malgus disarmed his opponent and attempted to stab her with his lightsaber. His attack was unsuccessful however, as Shan was able to absorb the energy from Malgus's lightsaber, essentially catching the blade. While the Sith attempted to penetrate the Jedi's defenses, he was tackled by Malcom, whom he had faced earlier. While they grappled, the Havok commander activated a grenade, sparking a blast that threw the two combatants apart, and grievously injured both.
Jace Malcom was rendered unconscious, though Malgus quickly recovered. Despite surviving the explosion, the Sith Lord was again assaulted by Satele Shan, who threw him with the Force into a large rock face. As Malgus struggled against her telekinetic attack, the Jedi mustered power through the force and delivered a powerful Force Wave, impacting the Sith Lord and shattering the rock around him. With the Imperial commander incapacitated, Republic forces continued to wipe out the Sith forces both in the forest battle and across the rest of Alderaan. Malcom later recovered to find the Imperials defeated, along with many of his own men. Upon being joined by his savior Shan, the commander fired a signal flare into the sky to indicate the Republic victory. The flare was matched by dozens of others across the planet that were immediately followed by the arrival of the Republic fleet, which had returned from addressing Malgus's diversion.
The return of the Republic's naval forces prompted the surviving Sith invaders to initiate a full retreat from the Alderaan theater. The seriously wounded Darth Malgus was rescued from the battlefield by his subordinates and loaded into his personal shuttle, bound for safer regions. While the Sith Lord recovered in his escaping vessel, he felt the presence of a Jedi in the ruins of a township destroyed by the orbital bombardment. Furious over the failure of his invasion, Malgus was determined to take the life of the Jedi in revenge. The Sith Lord ordered his pilot to reduce their speed and lower the shuttle before he jumped from the airborne vessel into the streets of the devastated town. With the full might of the Republic Military focused on Alderaan, the Sith were driven from the planet and the royal family was rescued from swtor Credits captivity.