The Lord was opposed to the Amalekites for two reasons. Firstly, they were a wicked people (1 Samuel 15:18) and thus deserving of God’s judgment.1 Secondly, they were opposed to Israel and constantly sought to destroy God’s people (see Exodus 17:8–15; Deuteronomy 25:17–19; Numbers 14:43–45; Numbers 24:20; Judges 3:13; Judges 6:3; Judges 10:12; 1 Samuel 14:48; 1 Samuel 30:1; 2 Samuel 8:12; Psalm 83:2–7). As a result, the Lord pronounces herem or the ban upon them (see Leviticus 27:28; Deuteronomy 20:16–18); this is the only occurence of this Hebrew term in Samuel.2 The herem involved destroying all people, and sometimes animals (livestock were not always included under the ban, Deuteronomy 2:34–35; Deuteronomy 3:6–7; Joshua 8:2; Joshua 8:26–27; Joshua 11:14) thereby devoting them to the Lord.3
3 Va maintenant, frappe Amalek, et dévouez par interdit tout ce qui lui appartient; tu ne l'épargneras point, et tu feras mourir hommes et femmes, enfants et nourrissons, bœufs et brebis, chameaux et ânes.