Related Rule
Ukraine
Practice Relating to Rule 46. Orders or Threats That No Quarter Will Be Given
Ukraine’s IHL Manual (2004) states:
1.3.2. The following methods of warfare shall be prohibited: … ordering that there shall be no survivors, to threaten an adversary therewith.
1.8.5. Serious violations of international humanitarian law directed against people include: … declaring that no quarter will be given. 
Ukraine, Manual on the Application of IHL Rules, Ministry of Defence, 11 September 2004, §§ 1.3.2 and 1.8.5.