929. Slaves
The decision of the invading forces to attack again didn't arrive due to a specific event. It was an inevitable choice made after they saw that the decades spent in peace had made them surpass their previous level.
After all, more than seventy years had passed since the end of the war. That time was enough to nurture promising cultivators from the human ranks to the heroic ones!
Even old monsters had managed to improve in that period thanks to the experience gained in the battles, the training areas built in the new territories, and the Divine Stele if they had a water aptitude.
The world never stood still. It always moved forward together with the powerful existences living inside it, and it wasn't unusual to see a positive trend after gaining access to so many resources.