Related Rule
Greece
Practice Relating to Rule 46. Orders or Threats That No Quarter Will Be Given
The Hellenic Territorial Army’s Internal Service Code (1984), as amended, provides: “It is forbidden for members of the armed forces: … To deny the unconditional surrender of the enemy.” 
Greece, Hellenic Territorial Army Regulation of Internal Service Code, Presidential Decree 130/1984 (Military Regulation 20-1), as amended, Article 15(c).
The Hellenic Navy’s International Law Manual (1995) provides:
[T]he prohibition of the methodology that there shall be no mercy for those captured during the hostilities or threats that none shall be captured alive serve the need to restrict casualties to the lowest possible level dictated by military necessity, even under the harsh conditions of armed conflict, avoiding exaggerations and outrages with a view to achieve a humane dimension against the inherent barbaric nature of war. 
Greece, International Law Manual, Hellenic Navy General Staff, Directorate A2, Division IV, 1995, Chapter 5, § 7.