The Skulken War

Overview
The Skulken War is the first major conflict in the Legends of Ninjago series, starting in the year 1885 and ending in the year 1889.

The Beginning of the War
The Skulken War was instigated by Lord Garmadon in the year 1885 (Ninjagian timeline) when the now notorious warlord made a deal with the ruler of the Skulkens, King Samukai. He supplied an army of undead skeleton soldiers in exchange for unknown reasons. Their conquest began in the Southern tip of Ninjago and they made their capitol in Wayport City where they built the towering fortress known as the Undead Citadel.

The Emperor of Ninjago was quick to respond to this threat and sent a counterforce to the South almost immediately. However, despite their best efforts, the most the Empire could do was slow them down. By 1889, Garmadon had reached the Jade River, halfway up the island of Ninjago.

The End of the War
A little known player in the war was an old veteran named Master Wu Garmadon. From 1885 to 1889 he became the military advisor to the Emperor. His main base of operations was the Yama Dera Monastery, gifted to him by the monarchy.

He knew that Garmadon was almost unstoppable and there was only hope for Ninjago: the ancient Golden Weapons crafted by The First Spinjitsu Master. And there were only four people on the island who could wield them.

So, Master Wu, using his Emperor-given resources, secretly went out and found four young boys: Cole Becket, Jay Walker, Kai Rayson, and Zane Julien. Once the boys were assembled, they and Wu’s two other students—Ann Jing and Keaton Haruto—set out, under the radar, to retrieve each weapon at their respective hiding places: The Frozen Wastelands, The Caves of Despair, The Sky Temple, and The Fire Temple.

After finding all four weapons, Master Wu and his students headed for the Underworld, the paranormal home of the Skulkens. Garmadon and King Samukai died during a fight with Master Wu, and the veteran returned to his Emperor with the good news.

Following the War
With their leaders gone, the Skulken army was scattered and disorganised. The Imperial Army pushed them back all the way to Wayport City, where the last remaining Skulkens held up in the Undead Citadel.

No one ever knew about what Wu or his students had done. In fact, no one knew that Wu even had students. The country celebrated their sudden victory as nothing more than a stroke of luck, and the healing process began.