Origin

The Mandalorians were a clan-based warrior culture known for their advanced weaponry, incredible training, and unmatched tenacity in combat.

The Mandalorian Wars started after the hordes of Mandalorian clans invaded Republic space. The Mandalorians first invaded Dxun, a moon of Onderon. The Republic would not face the invaders, so the Mandalorian leader, Mandalore, began ruthless attacks on helpless civilians on the planet Onderon. The Republic finally intervened, yet the Mandalorians won planet after planet.

The Mandalorian Invasion

In year 3,965 BBY, a warrior army known as the Mandalorian Neo-Crusaders began raiding worlds on the edge of the galaxy. After 20 years conquering non-Republic worlds they invaded Republic space and attacked the Onderon moon of Dxun. They then continued to attack Republic worlds with great ease.

They started their "crusade" in Dxun, where the Mandalorian leader Mandalore, created a military outpost in the heart of the moon's dense jungles. After the invasion of Dxun and Onderon, the Mandalorians began attacking the nine Iridonian worlds in the Outer Rim.

The next targets were the crystal cities of the planet Socorro, the woods of Eres 3, the cities of Duro, the Corellian worlds, the Venjagga system, the city-world of Taris, and Dagary Minor.

The battles here were mentioned in the Star Wars videogame Knights of the Old Republic 2: The Sith Lords (KotOR 2). The other dates, tales and facts are mentioned or happened in both games of the KotOR saga.

The Jedi intervene

The Republic begged the Jedi Council to enter the war; however, the Jedi were slow to act. The Council believed that the true threat had yet to reveal itself, and thus refused to assist the Republic and forbade its members to go to war. Two young Jedi Knights Revan and Malak decided to take action, calling for support from the ranks of Jedi who considered the Council to be making a mistake. Many Jedi Knights answered this call to follow the ingenious, charismatic Revan. Some of these Jedi were Xaset Tarep, Arren Kae, Nisotsa, Talvan Esan or Cariaga Sin, and the famous Jedi Exile. The Republic eagerly accepted this support, and so the war 'truly' began. The Jedi members who joined Revan and Malak in the war became generals and led Republic armies to fight the Mandalorians with the help of Republic soldiers such as General Derred, Mon Halan and Admiral Saul Karath, both of them traitors following Revan to the Sith. This was 3961 BBY and the battle between Jedi and Mandalorian ended one year later.

Revan proved to be one of the greatest tactical geniuses in galactic history, willing to make sacrifices to bring greater victories and was able to almost always outmaneuver the Mandalorians both on the ground and in space. Republic forces took incredible casualties throughout the war, in many cases losing as many as ten to twenty soldiers for every Mandalorian, but Revan's leadership managed to carry them through victory after victory, pushing the Mandalorians back to Yavin, across Korriban, out of Dxun and Onderon (where Exile lost a lot of soldiers due to droids and bombs, and where Revan won, destroying droids and mandalorian technology) and back into Mandalorian space.

The war ended at Malachor V. Revan led the battle from Trayus Sith Academy and there he confronted and defeated Mandalore the Ultimate. Revan had sent a massive fleet of Republic soldiers and Jedi whose loyalty was in question. Unknown to either side, Revan had hidden a weapon known as a "Mass Shadow Generator," designed by Zabrak engineer Bao-Dur, on the planet. Overseeing its use was the Jedi Exile, one of the Jedi who followed Revan to war and became one of his top Generals. The Exile gave the command to Bao-Dur to activate the weapon, and in doing so, watched as the Mandalorian and Republic fleets alike destroyed, crashing into and nearly destroying the entire planet.

Aftermath

Few men in either fleet survived this final battle. It marked Revan's final move before truly falling to the dark side. This terrible act of destruction caused the Jedi Exile to lose his connection with the Force, thus causing a hole within the Force. He was the only person out of all who followed Revan to turn from the dark side, and returned to the Jedi Council on Coruscant. The Council exiled him for following Revan to war, but their true reasons were quite different. They feared the hole within the Force that formed within him, and furthermore feared the failings in the Jedi teachings that he represented. Defiantly stabbing his lightsaber into the centerstone of the Jedi Council, as if it represented the failing of their teachings, the Exile left for the outer rim.

On the surface of Malachor V, Revan found the ancient Trayus Academy, a former Sith stronghold deeply marked with the dark side. Here he was corrupted by the Sith teachings. Revan and Malak were hailed as heroes within the Republic. Revan left with his fleet, reportedly to pursue the final remains of the Mandalorian fleet, but in truth searching for the ancient Star Forge. One year later, Revan and Malak returned at the head of a massive Sith armada, the Jedi and Republic soldiers who had once followed him now Sith. So began the Jedi Civil War.