War for the Sake of Peace
בענין המלחמה כי תצא כו' לא תירא מהם כו' ה"א עמך המעלך מא"מ כו'
Regarding the war of "When you go out" (Devarim 20), "do not be afraid of them," for "Hashem your God is with you, who brought you up out of the land of Egypt."
The parsha of going out to war assures Bnei Yisrael not to fear the enemy, because Hashem, who took them out of Mitzrayim, is with them.
כי הנה בנ"י יצאו מא"מ להיות צבאות ה' כמ"ש יצאו כל צבאות ה' מארץ מצרים וכתי' וחמשים עלו מזויינים שנעשו גבורי חיל להלחם מלחמות ה' ועיקר המלחמה שלהם הי' לברר מלכותו ית"ש ולעקור ע"ז מעולם
For behold, Bnei Yisrael went out of the land of Egypt to be the legions of Hashem, as it is written, "All the legions of Hashem went out of the land of Egypt" (Shemos 12:41), and it is written, "And the Bnei Yisrael went up armed" (Shemos 13:18) — that they became mighty warriors to wage the wars of Hashem; and the essence of their war was to make clear His kingship, may His Name be blessed, and to uproot idolatry from the world.
Bnei Yisrael left Mitzrayim specifically to serve as Hashem's army, becoming warriors whose true mission was to establish His kingship and remove idolatry from the world.
וז"ש שמע ישראל כו' כי כל המלחמה הי' לברר יחוד השם שבנ"י נבראו להעיד עליו ית' כמ"ש אתם עדי
And this is the meaning of "Hear, O Yisrael" (Devarim 20:3) — for the entire war was to make clear the Oneness of the Name, since Bnei Yisrael were created to bear witness to Him, may He be blessed, as it is written, "You are My witnesses" (Yeshayahu 43:10).
The call of "Shema Yisrael" before battle shows that the whole purpose of the war was to clarify Hashem's Oneness, for Bnei Yisrael exist to testify to Him.
ולכן צריכין ללחום עם אויבי ה' המשקרים במלכותו ית"ש ומכחישין עדות בנ"י
Therefore they must wage war against the enemies of Hashem, who falsify His kingship, may His Name be blessed, and who deny the testimony of Bnei Yisrael.
Because their role is to testify to Hashem's kingship, they must fight those who deny that kingship and contradict their testimony.
וז"ש על אויביכם להיות להם שונאים בהחלט
And this is the meaning of "against your enemies" (Devarim 20:3) — to be utterly hostile to them.
The phrase "against your enemies" teaches that these foes are to be regarded with complete and absolute hostility.
כמ"ש אין שנאה כשנאת הדת כי לא הי' המלחמה שלהם לצורך המדינה רק לעקור מהם עבודה זרה
As they said, "There is no hatred like the hatred of religion," for their war was not for the needs of the state, but only to uproot idolatry from among them.
This hostility flows from the clash over emunah itself, not from political interests, since the goal was only to eliminate idolatry.
וכן הי' הדין אם השלימו שלא לעבוד ע"ז היו מקבלין אותן
And so was the law: if they made peace, that they would not serve idolatry, they would accept them.
If the enemy agreed to abandon idolatry and make peace, the halachah was that they would be accepted rather than fought.
ולכן הקדימו קודם המלחמה השלום כמ"ש וקראת אלי' כו' לברר כי כל המלחמה שלהם לצורך השלום כמ"ש אני שלום וכי אדבר המה למלחמה
Therefore they put the offer of peace before the war, as it is written, "And you shall call out to it [in peace]" (Devarim 20:10), to make clear that their entire war was for the sake of peace, as it is written, "I am peace, but when I speak, they are for war" (Tehillim 120:7).
Because the aim is peace, the Torah requires offering peace before waging war, showing that the war itself is ultimately for the sake of peace.
פי' שכל מלחמה שלנו בעבור שהם מעכבין השלום בעולם כמ"ש שאין שמו שלום עד שימחה זרע עמלק וסתם מלחמה הוא עמלק ושאר הרשעים שנמשכו אחריו כמ"ש ראשית גוים עמלק ולכן תכלית מלחמתן של בנ"י הוא השלום כנ"ל:
The explanation is that every war of ours is because they hold back peace in the world, as it is said, that His Name is not "peace" until the seed of Amalek is wiped out; and "war" without qualification refers to Amalek and the other wicked ones who follow after him, as it is written, "Amalek is the first of the nations" (Bamidbar 24:20) — and therefore the ultimate purpose of the war of Bnei Yisrael is peace, as explained above.
Every war Bnei Yisrael wage is because the wicked, with Amalek at their root, obstruct peace in the world; thus the final goal of their wars is peace itself.
Summary: The Sfas Emes explains that the wars of Bnei Yisrael described in parshas Shoftim were never about land or political gain, but about clarifying the kingship and Oneness of Hashem and uprooting avodah zarah from the world. Bnei Yisrael went out of Mitzrayim to be the legions of Hashem, created to bear witness to Him, so they must contend with those who deny His kingship and contradict that testimony — a hostility rooted in emunah rather than worldly interest. This is why the halachah requires offering peace first and accepting any enemy who agrees to abandon idolatry. The deeper point is that Hashem's Name is not complete as "peace" until the seed of Amalek, the root of all wickedness, is wiped out. Therefore the ultimate purpose of every war of Bnei Yisrael is peace itself.