What is the origin of the idiom "marching orders" and when to use it?

The origin of the idiom "marching orders" can be traced back to military terminology. In military operations, "marching orders" referred to the specific instructions given to soldiers regarding their movement, formation, and objectives. It provided clear guidance on the route, timing, and actions required during a march or campaign. It is commonly used in professional settings, such as workplaces, military operations, sports teams, or project management.