Imperial Decree of declaration of war against foreign powers

When two countries don't like each other very much, sometimes they decide to fight each other. This is called a war. The person who is in charge of a country, like a king or a queen, can officially tell their country's soldiers to go fight the soldiers from the other country. This official message is called an imperial decree of declaration of war against foreign powers. It means that the leader of the country is saying "we are now at war with this other country, and we need to send our soldiers to fight them." The imperial decree is a really important message because it can change a lot of things in a country - soldiers might have to leave their families to go fight, and lots of other people might have to start working really hard to help the soldiers win the war. So it's very serious and important when a leader declares war through an imperial decree.