This study enrolled women who had been diagnosed with breast cancer within the past five years to help researchers develop and test a mobile phone app to help breast cancer survivors increase their physical activity. The app developed in this study will be tested in a clinical trial that will help the researchers determine if its use increases breast cancer survivors’ physical activity levels. Army of Women recruitment opened on February 24, 2016, and focused on enrolling breast cancer survivors in the Chicago, Illinois area. After 24 women expressed interested, the research team decided to open enrollment to survivors throughout the US on March 9, 2016. Within 24 hours, 196 women expressed interest in participating and the research team closed enrollment.