אלף למטה אלף למטה. יש אומרים, אלפים מכל שבט ושבט שלח. ויש אומרים, שלשת אלפים מכל שבט ושבט. שנים עשר אלף חלוצי צבא, ושנים עשר אלף לשמור את הכלים, ועליהם הוא אומר, שניך כעדר הקצובות וגו'. ושנים עשר אלף לתפלה. ומנין. שכך כתיב, אלף למטה אלף למטה, הרי שני אלפים. וימסרו מאלפי ישראל. מהו וימסרו. שהם נמסרין זוגות זה לזה.
When describing the conscription for the war with Midian, the Torah says that each tribe will provide one thousand soldiers, and the Torah repeats the words: Elef Lamatteh, elef lamatteh. The Medrash explains the repetition (and the word וימסרו) to mean that besides the thousand soldiers conscripted from each sheivet, an additional two thousand people were separated from each sheivet. Each soldier had two people assigned to him. These were one for support, like providing food and transportation, and one to daven and learn Torah as a merit to keep his soldier safe.
Rav Elyashiv shlit"a (דברי אגדה p.321) brings this Medrash (Bamidbar Rabbah 22:3) and says that this requirement of tefilla, having one person davenning for the safety and success of each soldier, was for a battle that was declared explicitly by Hashem and so was predestined to be successful. Additionally, we add the leadership of Pinchas, the call of the chaztotzros and the presence of the Aron Hakodesh and the Tzitz of the Kohen Gadol. Also, we can also assume that the Dor Dei’ah as a whole, all the people who davenned every day during the war as they always davenned, knew how to daven for the success of the war and said tehillim for safety and success. Despite all that siyata dishmaya, Moshe earmarked for each and every soldier a meilitz yosher. One can only imagine that in our time, writes Rav Elyashiv, we should have 10 people davening and learning (Torah magna umatzla, Sotah 21a,) for the safety of every single soldier.
See also Makkos 10a:
During that war, the Arutz 7 News Organization printed this article about this project, and quoted the Bostoner Rebbe, and yibadlu lechaim Rav Simcha Kook and Reb Chaim Kanievsky as strongly supportive.
Although this idea became well known in '09, my sister, Rebbitzen Faskowitz of Queens, who is married to Rabbi Moshe Faskowitz of the Torah Center of Hillcrest, wrote an article that was printed in the Jewish Press, suggesting this idea during the 2006 war in Lebanon, that people should have the name of a specific soldier for whom to be mispallel for success and safety. It's a lot more effective when you're being mispallel and learning for a specific person with a name that you know, especially when he is putting himself in harm's way to protect you. The least you can do is daven and learn to protect him.
Baruch Hashem, there's no hot war going on. But soldiers are still being conscripted and soldiers are still endangered, and they're doing their job to protect the yishuv in Eretz Yisrael. It is still a good idea to have the name of a specific soldier in mind. Since individuals cannot do this, and the Elef Lamateh organization is not currently in business, I would suggest that shuls figure out how many mispallelim they have, men and women, and get an equal number of names from a contact in Israel, who will circulate a form on Facebook or something like that in which soldiers who consent to the arrangement can submit their names, and then assign a soldier to each and every single adult in the shul. Keep track of your soldier! If you want to send him a salami or her a box of cookies, that would be fine, too, but don't let that get in the way of your real job- protecting him or her with your Tefilla and Torah.
I recently became aware of a Sicha attributed to Harav Weintraub in which he shares with us a strikingly different perspective. I think that you can see that his primary concern is that one might develop a sense of parity or privity with people who hate the Torah and the Halacha. On that basis, he makes a policy decision, as you will see, and policy decisions are not always pretty. I found it on the Life in Israel blog. You will have to click on each picture to make it comfortable to read.