Someone whose livelihood is war. A word established along with the expansion of the war economy, in line with the terms white-collar and blue-collar.
The phrase "white-collar" stems from white shirts and is used to refer to administrative or intellectual workers.
On the other hand, "blue-collar" stems from blue work clothes and is used to refer to manual laborers.
In contrast to the two terms, "green-collar" comes from the image that most military personnel and soldiers wear green (khaki) uniforms.