Now, it’s worth noting that the definition of “combat-related” is quite broad. If you got blown up by an IED in Iraq and received a Purple Heart, you absolutely qualify. But many veterans could qualify for CRSC if they were exposed to toxic chemicals or got badly injured in training.
Agent Orange-related illnesses are considered combat-related under the “instrumentality of war” clause of CRSC. In plain English, that means you were exposed to instruments of war, including chemical agents. Exposure to burn pits, radiation, and Gulf War disease could also qualify you for CRSC, if they caused you to develop a chronic illness.
Broadly speaking, any disability presumed to be service-connected (think Agent Orange in Vietnam or burn pits in Iraq and Afghanistan) could be considered combat-related for CRSC purposes.
Unfortunately, medical retirees with less than 20 years of service are not eligible for CRDP as of this writing.