(ב) רַבִּי חֲנִינָא סְגַן הַכֹּהֲנִים אוֹמֵר, הֱוֵי מִתְפַּלֵּל בִּשְׁלוֹמָהּ שֶׁל מַלְכוּת, שֶׁאִלְמָלֵא מוֹרָאָהּ, אִישׁ אֶת רֵעֵהוּ חַיִּים בְּלָעוֹ.
(2) Rabbi Hanina, the vice-high priest said: pray for the welfare of the government, for were it not for the fear it inspires, every man would swallow his neighbor alive.
There is no question that, in Jewish law, military service, when it is required by the government, must be accepted wholeheartedly by subjects or citizens of Jewish faith. The duty to respect the commands of the government is clearly stated and emphasized in Jewish law. This attitude of respect and loyalty to the government is summarized, for example, in the introductory statement of Isaac Elchanon Spector's "Eyn Yitzchok Hasheni"... The specific duty to serve in the army is described in detail by the Chofetz Chaim (Israel Meir Hacohen of Radun) in his Introduction to "Machane Yisroel": "It is a great sin," he says, "to evade service in the army."
adapted from http://www.behrmanhouse.com/sites/default/files/post/Mark%20H%20Levine/Julian%20KafkaEthics%20of%20war-final.docx
Wars are categorized as one of three permissible types-
Milchemet Hovah- mandatory war
- These are the wars of the original conquest of the Land of Israel by the Israelites under the command of Joshua and later the Judges and finally Saul and David. These were the wars that fulfilled the promise of God’s land going to the descendants of Abraham, Isaac and Jacob.
- These are wars to expand the boundaries of the nation or to enlarge the nation’s treasure. These wars require permission. A milchemt reshut requires the permission of the Sanhedrin - the full rabbinic judicial body of seventy - to say that the war is permissible to fight. The rabbis according to Maimonides have to gauge the will of the public to support the war.
- The milchemet mitzvah is the obligatory war of self-defense. A defensive response is not only permissible, it is mandatory—citizens are required to defend their nations and families from attack – even a pre-emptive strike if the enemey is at their border.
(א) אֵין הַמֶּלֶךְ נִלְחָם תְּחִלָּה אֶלָּא מִלְחֶמֶת מִצְוָה. וְאֵי זוֹ הִיא מִלְחֶמֶת מִצְוָה זוֹ מִלְחֶמֶת שִׁבְעָה עֲמָמִים. וּמִלְחֶמֶת עֲמָלֵק. וְעֶזְרַת יִשְׂרָאֵל מִיַּד צָר שֶׁבָּא עֲלֵיהֶם. וְאַחַר כָּךְ נִלְחָם בְּמִלְחֶמֶת הָרְשׁוּת וְהִיא הַמִּלְחָמָה שֶׁנִּלְחָם עִם שְׁאָר הָעַמִּים כְּדֵי לְהַרְחִיב גְּבוּל יִשְׂרָאֵל וּלְהַרְבּוֹת בִּגְדֻלָּתוֹ וְשִׁמְעוֹ:
(ב) מִלְחֶמֶת מִצְוָה אֵינוֹ צָרִיךְ לִטּל בָּהּ רְשׁוּת בֵּית דִּין. אֶלָּא יוֹצֵא מֵעַצְמוֹ בְּכָל עֵת. וְכוֹפֶה הָעָם לָצֵאת. אֲבָל מִלְחֶמֶת הָרְשׁוּת אֵינוֹ מוֹצִיא הָעָם בָּהּ אֶלָּא עַל פִּי בֵּית דִּין שֶׁל שִׁבְעִים וְאֶחָד:
(1) A priori, the king does not go to fight other than a War of Mitzvoh (Mandatory War). What is a War of Mitzvoh? This is the war against the Seven Nations30Aboriginal to Eretz Yisroel. or the war against Amalek or any war to assuage Israel of a persecutor. After this, he may fight Discretionary Wars which are those wars he conducts against the other nations in order to enlarge the borders of Israel, and increase his renown and reputation31So that the Gentiles will be afraid of us and won’t bother us..
(2) He does not need to obtain permission from the Court to engage in a War of Mitzvoh but he may, at any time, on his own, compel the people to go out to war. However, he requires the authorization of the Court of Seventy-One to take the people with him go out to fight a Discretionary War.
O God, we come before You in gratitude for these men and women of the United States Armed Forces. Many served our country in years gone by. To them, we are indebted for the freedoms we enjoy today. Others continue in service at this hour, in Iraq, in Afghanistan, in San Antonio, and around the world. We are thankful for their many sacrificial acts on behalf of our great nation, particularly in the wake of war. Bless each of these men and women. Instill in them pride in their service, ever-increasing love of country, and enduring devotion to their sacred calling. Grant to each of them good health, loving families, and abiding faith in You, O God. Instill in all of us gratitude to our military, and to the husbands and wives, loving partners, mothers and father, sons and daughters, of all who serve. They, too, sacrifice for our beloved country, here and abroad. Let us all find inspiration in these men and women. May we affirm that devotion to Judaism and love of the United States go hand in hand. May we all stand ready to defend our country and the principles on which it stands, even as we are prepared to defend our Jewish people and our ancestral faith. Bless, O God, the men and women who stand before your holy ark. Bless the United States. Bless us all with your choicest blessing, the blessing of peace. Amen.