Related Rule
Practice Relating to Rule 39. Use of Cultural Property for Military Purposes
Croatia’s Commanders’ Manual (1992) states:
13. Specifically protected objects may not become military objectives …
14. The immunity of a marked cultural object may be withdrawn in case of imperative military necessity.
62. [In defence] the immunity of a marked cultural object shall only be withdrawn when the fulfilment of the mission absolutely so requires. The withdrawal shall only take place to the extent necessary. Advance warning and removal of distinctive signs shall make the situation clear to the enemy. 
Croatia, Basic Rules of the Law of Armed Conflicts – Commanders’ Manual, Republic of Croatia, Ministry of Defence, 1992, §§ 13–14 and 62.