KA0 AMRS: Auxiliary Military Radio Stations
[J2-7]  [J8]  [J9]  [JA]  [KA2]  [KA3]  [KA4]  [KA5]  [KA6]  [KA7]  [KA8]  [KA9]  [KA0]  [KA1]  [KG6I]  [KR6]  [KA b4 DU]  (callsign.jp)
Please inform me of any additional data, thank you. — Ryota "Roy" Motobayashi, JJ1WTL@JARL.COM
While KA0 is not reserved for AMRS nowadays — yes, KA2-KA9 2×2 call signs are only reserved — it was actually used in Iwojima I., in Ogasawara in our past.
ex-Call Call Licensee Address es-Call Source
KA0 — Iwo Jima I. (now JD1) 1950s
  KA0CY   Everett E. Worrell, Jr. Iwo Jima I. KA3CY
W4WJJ		 1956f-w-57sp-su-f;
Himself (1956-57)
  KA0IJ   Robert L. Green 1956th AACS Squadron, APO 815   1952w-53sp-su-f-w; AD1C (1953-); QSO Dec. 26, 1958
    Clayton Dalton Airways & Air Communications Service, Det. 1956-2, 1956th AACS Squadron, APO 815   1954sp-su-f-w-55sp-su-f-w-56sp-su-f-w-57sp-su
  KA0SC T.Sgt Scott H. Chase 1964 AACS Squadron, APO 815 (Iwo Jima I.)   K8CS Ham Gallery (QSO 1957); W8HVG qrz.com

References

[J2-7]  [J8]  [J9]  [JA]  [KA2]  [KA3]  [KA4]  [KA5]  [KA6]  [KA7]  [KA8]  [KA9]  [KA0]  [KA1]  [KG6I]  [KR6]  [KA b4 DU]  (callsign.jp)
Dec. 26, 2010, Ryota "Roy" Motobayashi, JJ1WTL