When Equestria was in danger and in dire need for a powerful self defence force, the elements of harmony did not prove to be effective weapons. They could banish princesses to the moon but they and their beares could not defeat entire armies.

Although these six ponies had always overcome whatever or whoever dared to raise its head against harmony and friendship time and time again, even they had a limit of what they were capable of accomplishing. The Royal wedding showed this to the world.

The changelings had broken the magical shield, which the ponies thought was impossible, and had been overruning the city. Despite the royal couple's best efforts, love alone could not defeat the invaders, and the elements, although present, soon had to realize that this fight could not be won with friendship alone. An entire regiment of changelings had persisted in the capital city of Equestria after the love blast and the fighting for the city raged on for a full month.

The changelings bravely held their ground against the royal guard, turning large parts of the city into smoking ruins. Since the banishment of princess luna, there had never been this much death and destruction in Equestria ever again. It was a rough wake up call for the ponies, who firmly believed that they could not be in any danger under the protection of the princesses. The trauma and bloody stain the changelings left on the city and the entirty of Equestria would persist and in the end be the turning point of history.

The battle ignited the spirit of resistance within the ponies. They did no longer want to be relying on others to protect them, they wanted to fight. Since changelings showed them the weaknesses of their heros, waves of new volunteers swept into the royal army and guard.

The battle for Canterlot was ultimately a loss for the changelings. The survivors fled the city with the weapons they had acquired, and peace returned, but the damage was done. The ponies lusted for a fight to prove themselves and the changelings seeked revenge. Fertile ground for conflict. And no creature tried to stop it as the world strays further and further away from any peaceful solutions.