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

The origin of the idiom "shoulder to shoulder" can be traced back to the physical act of standing or working in close proximity with one's shoulders touching. This literal representation of physical closeness and unity has been metaphorically extended to describe a sense of collaboration, support, and solidarity. The phrase likely emerged from observations of individuals standing shoulder to shoulder in military formations, where soldiers would align themselves closely to present a united front and enhance their collective strength. It is commonly used in team settings, whether in sports, professional environments, or community projects, to emphasize the importance of collaboration and collective effort.