Practice Relating to Rule 20. Advance Warning
Côte d’Ivoire’s Teaching Manual (2007) provides in Book III, Volume 1 (Instruction of first-year trainee officers):
IV.1.1. Obligations in the planning of offensive actions
Before concretely launching an attack which could have negative effects on the civilian population, the combatant will give advance warning in order to allow the population time to leave the area or at least to take shelter. The warning must, of course, be authentic and effective. It must reach the civilians for whom it is intended, leaving them sufficient time to react. The warnings can be distributed by radio or television, by dropping leaflets, or on the Internet. The force leading the attack can be dispensed from giving a warning if the circumstances do not allow it because it would compromise the purpose of the operation.
IV.3.2. The civilian population staying
The civilian population can choose to stay in a town under siege. …
If the civilians do not leave the town under siege, this does not signify that the commander who directs the attack is dispensed from his duties to take all the usual precautions listed above … Sure, violators could consider that it is in their interest to hold back the civilian population, or parts of that population, to serve as human shields, or to elicit the sympathy of the international opinion regarding the humanitarian situation of the population and thereby to discredit the enemy. Nevertheless, the force leading the attack can easily thwart these proceedings by respecting the law, giving warnings, giving time for an evacuation in the form of a ceasefire, and by ensuring that the civilians are granted passage in safe conditions towards a protected zone or place.
In Book IV (Instruction of heads of division and company commanders), the Teaching Manual provides:
Effective advance warning shall be given of attacks which may affect the civilian population, unless circumstances do not permit. For tactical reasons, an attacking force may not give a warning in order to preserve the element of surprise.