For national security reasons, the United States military does not announce its preparedness or DEFCON level to the public. To understand the different DEFCON levels and what DEFCON 3 means, you must first understand what DEFCON is short for. The defense readiness condition (DEFCON) described five gradual levels of readiness, increasing from one to five depending on the severity of the threat. On a scale that runs backward from five to one, DEFCON levels are: