What is the authors phrase The foster women made a fortress out of duty?

The phrase "The foster women made a fortress out of duty" suggests that the foster women created a strong and protective environment for the children in their care, despite the challenges they faced. The word "fortress" implies a sense of security and safety, while the phrase "made out of duty" indicates that the foster women felt a strong obligation to provide this care. This phrase highlights the dedication and commitment of the foster women in their role as caregivers.