What does it mean to be pressed into service?

Definition of press (someone or something) into service

: to use (someone or something) for a particular job or purpose when a special need occurs Retired doctors and nurses were pressed into service to help care for the wounded. The backup computer was pressed into service when the main computer failed.

What did being in-service mean?

The definition of in-service is something that happens while someone is a full-time employee. An example of in-service is the training a teacher receives to learn updated information about technology. adjective. 2. Of, relating to, or being a full-time employee.