| 1 | A | B | C |
| --- | --- | --- | --- |
| 2 | Operation Una - Order of battle |  |  |
| 3 | Corps | Unit | Notes |
| 4 | Zagreb | 1st Guards Brigade | In the area of Dvor |
| 5 | Zagreb | 2nd Guards Brigade | In the area of Hrvatska Dubica |
| 6 | Zagreb | 17th Home Guard Regiment | In the area of Hrvatska Dubica |
| 7 | Zagreb | General Staff Reconnaissance Sabotage Company | In Hrvatska Kostajnica |
| 8 | Bjelovar | 52nd Home Guard Regiment | In Jasenovac area, a battlegroup of 770 troops |
| 9 | Bjelovar | 121st Home Guard Regiment | In Jasenovac area, a battlegroup of 911 troops |
| 10 | Bjelovar | 125th Home Guard Regiment | In Jasenovac area, a battlegroup of 800 troops |
| 11 | Bjelovar | 16th Artillery-Rocket Brigade | One battalion of 155-millimetre (6.1 in) howitzers only, 237 troops |
| 12 | Bjelovar | 18th Artillery Battalion | A platoon of 155-millimetre howitzers and a platoon of 130-millimetre (5.1 in) gun, 106 troops |
| 13 | Bjelovar | 34th Engineer Battalion | Also utilising equipment of the 33rd Engineer Battalion |
| 14 | Bjelovar | 69th Military Police Company | - |

Question: Who  sent the 121st Home Guard Regiment battlegroup to Jasenovac, as reinforcement?
Answer: The Bjelovar Corps sent the 121st Home Guard Regiment battlegroup to Jasenovac, as reinforcement.