call to arms
nounUK /ˌkɔːl tʊ ˈɑːmz/
US /ˌkɔːl tʊ ˈɑːrmz/
A call to arms is a loud request for people to get ready to fight or help.
The king sent a call to arms across the land.
OTHER MEANINGS
2. A strong request for people to join a cause or effort.
The scientist's speech was a call to arms against pollution.
3. A signal, like a drum or bugle, telling soldiers to gather.
At dawn, the bugle's call to arms woke the camp.
4. A warning that danger is near and people must act.
The flood siren was a call to arms for the whole town.