Kampfgruppe Engelbrecht - German units training Croatian forces inside NDH

Feldpost card 23.01.1945 to Reich from Fp.02873B which is schwere Kompanie Kampfgruppe Engelbrecht,
  
Fp.02873 :
 (1.8.1943-23.3.1944) 21.12.1943 Stab u. 1.-4. Kompanie Deutsches Ausbildungs-Bataillon 1 bei 1. Kroat. Jäger-Brigade,
(7.11.1944-Kriegsende) 17.1.1945 Regimentsstab u. schwere Kompanie Kampfgruppe Engelbrecht, 

Kampfgruppe Engelbrecht  was formed at the end of 1944 or beginning of 1945 from German forces that were training Croatian army in NDH , it had stab and 3 batallions and fought in NDH :

Stab from   Deutsches Ausbildungs-Bataillon 1 bei 1. Kroat. Jäger-Brigade,
 Fp: 02873 Regimentsstab u. schwere Kompanie Kampfgruppe Engelbrecht,

I. batallion from Deutsches Ausbildungs-Bataillon. 4. der 4. kroat.Jäger-Brigade.
Fp.04450 Stab I u. 1.-4. Kompanie Kampfgruppe Ingelbrecht
 
II. batallion from Deutsches Ausbildungs-Bataillon. 4. der 4.kroat.Gebirgs-Brig.;
Fp 05173 Stab II u. 5.-8. Kompanie Kampfgruppe Ingelbrecht.

III.batallion from Deutsches Ausbildungs-Bataillon. 3. der 3.kroat.Jäger-Brigade
Fp 07571 Stab III u. 9.-12. Kompanie Kampfgruppe Engelbrecht

  It is possible that  Sturm-Brigade Südost  is formed in  3-4/1945 from  Kampfgruppe Engelbracht. (or  maybe gruppe Fischer? at the end of the war a lot of "ad-hoc" fighting groups were formed that are poorly documented and it is impossible to reconstruct their origins completly)