Ordnance is another word for military supplies, like guns, rockets, or armor. When a country is at war, it needs a lot of ordnance.
The average person has probably never heard of ordnance. In fact, an ordinary person would have some explaining to do if they had ordnance, because it refers to military supplies. The word ordinance for “command” lost an i in the 1500’s and became ordnance, meaning “military materials.” Both words go with war — a command to shoot requires ordnance, or something to shoot with. Ordnance helps soldiers fight and protect them. You can’t go to war without ordnance.