to the contrary , and provided that the claimed stressor is consistent with the circumstances , conditions , or hardships of the veteran ' s service , the veteran ' s lay testimony alone may establish the occurrence of the claimed in - service stressor . VA has consistently defined " engaged in combat with the enemy " to require a veteran have participated in events constituting an actual fight or encounter with a military foe or hostile unit or instrumentality . See VAOPGCPREC 12 - 99 ( October 18 , 1999 ) . For stressors unrelated to combat , credible supporting evidence is necessary in order to grant service connection . " Credible supporting evidence " of a noncombat stressor may be obtained from service records or