exemptions from the draft

12,000 soldiers, 1000 from each sheivet, went out to war against Midian.  אֶלֶף לַמַּטֶּה אֶלֶף לַמַּטֶּה לְכֹל מַטּוֹת יִשְׂרָאֵל תִּשְׁלְחוּ לַצָּבָא.  Rashi comments based on Sifri לכל מטות ישראל – לרבות שבט לוי.   (Parenthetically: Shouldn't there be 13,000 then?  Mizrachi answers that Ephraim and Menashe count as 2 shevatim viz a viz getting nachala in Eretz Yisrael, but here they are counted as one.  See Gur Aryeh.  The Sefas Emes in Likutim has a chiddush gadol that the 12,000 are apart from sheivet Levi.  The entire sheivet Levi -- all 22,000 of them -- actually reported for duty to escort the aron.)

Unless you've had your head in the sand the past few weeks you know that the issue of the exemption of hareidi yeshiva students from the draft in Israel is once again being debated.  One of the most widely cited sources on the issue is the Rambam at the end of hil shemita, who exempts sheivet Levi from military duty:

ולמה לא זכה לוי בנחלת ארץ ישראל ובביזתה עם אחיו מפני שהובדל לעבוד אתה׳ לשרתו ולהורות דרכיו הישרים ומשפטיו הצדיקים לרבים שנאמר יורו משפטיך ליעקב ותורתך לישראל. לפיכך הובדלו מדרכי העולם לא עורכין מלחמה כשאר ישראל ולא נוחלין ולא זוכין לעצמן בכח גופן. אלא הם חיל השם שנאמר ברך ה׳ חילו. והוא ברוך הוא זוכה להם שנאמר אני חלקך ונחלתך:

Rambam continues and writes that not only is Levi exempt, but anyone who wants to take on the role of full time Torah study/teaching like Levi is exempt as well:

ולא שבט לוי בלבד אלא כל איש ואיש מכל באי העולם אשר נדבה רוחו אותו והבינו מדעו להבדל לעמוד לפני ה׳ לשרתו ולעובדו לדעה את ה׳ והלך ישר כמו שעשהו האלהים ופרק מעל צוארו עול החשבונות הרבים אשר בקשו בני האדם הרי זה נתקדש קדש קדשים ויהיה ה׳ חלקו ונחלתו לעולם ולעולמי עולמים ויזכה לו בעה"ז דבר המספיק לו כמו שזכה לכהנים ללוים. הרי דוד ע"ה אומר ה׳ מנת חלקי וכוסי אתה תומיך גורלי:

It seems that Rambam disagrees with Rashi's position that even sheivet Levi went to war.  

The two views find their roots in different girsaot in the Sifrei.  The Sifri as we have it reads להביא את שבטו של לוי; but the GRA changes the girsa to להוציא שבט לוי.

(The Rogatchover suggests that the battle against Midyan was an act of nekama, not technically a milchama, so perhaps Rashi here is not a proof as to whether sheivet levi was obligated to enlist in other cases.  The downside of this approach is that it means the Sifri cannot serve as a makor for the Rambam, and so one must find some other source for this tremendous chiddush that Rambam advances.)

Were the issue that simple : )

The problem is that it is hard to take this Rambam at face value.  Rambam writes in hil melachim ch 7:

ואחר שחוזרין כל החוזרין מעורכי המלחמה. מתקנין את המערכות. ופוקדים שרי צבאות בראש העם. ומעמידין מאחור כל מערכה ומערכה שוטרים חזקים ועזים. וכשילין של ברזל בידיהם. הרוצה לחזור מן המלחמה הרשות בידן לחתוך את שוקו. שתחלת נפילה ניסה. במה דברים אמורים שמחזירין אנשים אלו מעורכי המלחמה במלחמת הרשות. אבל במלחמת מצוה הכל יוצאין ואפילו חתן מחדרו וכלה מחופתה:

אחד המארס את הבתולה. ואחד המארס את האלמנה. וכן אם נפלה לו יבמה אפילו חמשה אחים ומת אחד מהן כולן חוזרין. קדש אשה מעכשיו ולאחר שנים עשר חדש ושלם הזמן במלחמה חוזר ובא לו:

המחזיר את גרושתו. והמארס אשה האסורה עליו. כגון אלמנה לכהן גדול. גרושה וחלוצה לכהן הדיוט. ממזרת ונתינה לישראל. בת ישראל לממזר ולנתין. אינו חוזר:

The Rambam writes that הכל יוצאין - everyone goes out to war, even a chassan and kallah. He speaks of  כגון אלמנה לכהן גדול. גרושה וחלוצה לכהן הדיוט going to battle. Were there a blanket exemption for members of sheivet Levi from war, what is the kohen gadol or hedyot doing here?

Furthermore, the gemara (Kid 21) discusses whether a kohen is permitted to take a yefat toar.  The Ramban paskens (8:4)

הכהן מותר ביפת תואר בביאה ראשונה. שלא דברה תורה אלא כנגד היצר. אבל אינו יכול לישאנה אחר כך מפני שהיא גיורת

Again, how does this make sense if members of sheivet Levi do not go to war?

Not only do we see that kohanim serve, but we find in Tanach that בניהו בן יהוידע, who was a kohen (Divrei haYamaim I 12:28), was appointed by Shlomo as a general in charge of his army (Melachim I 2:35)!

Finally, and more fundamentally, it is strange that the Rambam brings up this exemption of sheiveit Levi from war at the end of hil shemita but makes no mention of it in hil melachim where he codifies all the other laws that pertain to battle.    

Some argue based on this consideration that the Rambam at the end of hil shemita is not meant to be taken as a halachic statement.  The Ramban often concludes a sefer with a mussar or philosophical point.  Here too, the Rambam is just setting a goal of a high level of talmud torah for us to aspire to, not lay down the practical rules of who should or should not go out to war.  

If so, there is no argument between Rashi and the Rambam, and this Rambam cannot serve as a source to exempt yeshiva students from the draft.

Others do accept that there is an exemption from battle for sheivet levi, but qualify that exemption in some way so as to allow a scenario of kohanim participating in battle. You can read this article for a rundown of the various chilukim that aim to get to this result.  Since I have a day job and limited time, I'll just mention one: When an army goes to war, not everyone gets called up at once and not everyone is deposited on the front lines at once.  The army drafts based on its needs.  The Brisker Rav (Sota 43) therefore suggests that in principle, sheivet Levi has a chiyuv to participate in war like anyone else.  What the Rambam in hil shemita means is that given the option, we defer drafting kohanim and leviim until we have exhausted all other options.  

It's interesting that this Rambam that everyone quotes as the source to exempt people from battle never uses the words פּטורים מללכת למלחמה!  What he says is לא עורכין מלחמה כשאר ישראל - sheivet levi does not go to war like everyone else.  There is a big difference between saying that levi does not going to war, period, full stop, and saying that they do not going to war **like other people**.  I would certainly hope that when bnei Torah go to war, they don't go like everyone else.  I think the plain meaning of the words is exactly like the chiddush of the Brisker Rav.  Sheiveit levi does go to war, but the criteria for when and how they are drafted is different than that of other shevatim, as indeed it should be.   

On a practical level, it's important to also mention that one thing is certain: the burden of להבדל לעמוד לפני ה׳ לשרתו is not a light one.  For example,  it seems reasonable to me to assume that the Rambam's standard does not allow for a multi-week bein ha'zemanim vacation away from sedarim.  להבדל לעמוד לפני ה׳ לשרתו is a full time 24x7 occupation, a life of total dedication to Torah and ruchniyus.  Thus, even if one accepts the theoretical possibility of there being an exemption from the draft, practically speaking it is hard to see how the bar set by the Rambam can be met by any more than a small minority of 18-19 year olds.  I haven't met too may young men who have achieved such lofty heights of holiness at such a young age, but then again, maybe my experience is too limited. 

It's also worth remembering that at the end of the day, many of those who leave beis medrash to serve also share the aspiration להבדל לעמוד לפני ה׳ לשרתו.  Our ultimate ideals are the same, even if we disagree sharply in the messy practicalities of how to achieve them.