A tradition

sonatagreen:

In peacetime, the ruler grows their hair long. In war, they cut it short.

A ruler with long hair is held in great esteem, for defending the peace.

The traditional declaration of war is for the ruler to send their cut-off hair to the enemy ruler. The statement carries greater weight the longer the hair: to receive long hair says that you have angered one who is slow to anger, that you have incurred a wrath not easily woken.