U.S. Army Reserve Soldiers prepare to extract a mannequin victim from underneath a vehicle May 6, 2017 at Muscatatuck Urban Training Center, Indiana. Nearly 4,100 Soldiers from across the country are participating in Guardian Response 17, a multi-component training exercise to validate U.S. Army units' ability to support the Defense Support of Civil Authorities (DSCA) in the event of a Chemical, Biological, Radiological, and Nuclear (CBRN) catastrophe.