What should a sentry do when encountering someone on their post without proper authority, according to the 11th General Order?

The correct action for a sentry when encountering someone on their post without proper authority is to challenge them. This aligns with the 11th General Order, which emphasizes the responsibility of a sentry to allow only authorized personnel to pass and to challenge anyone whose identity or purpose is in question.

Challenging an unauthorized individual ensures the security and integrity of the post, preventing potential threats or breaches. A sentry is trained to maintain vigilance and to assess situations critically. It's essential to remember that the duty of the sentry includes not only ensuring the safety and security of the area but also taking immediate action when protocol is not being followed.

Allowing someone to pass based on their appearance could compromise security, as trustworthiness cannot be determined by initial impressions alone. Ignoring the presence of an unauthorized person fails to uphold this responsibility and can lead to significant risks. Calling for help may be warranted if the situation escalates, but the immediate response should focus on challenging the individual to ascertain their intentions and authority to be in the area.