Go to this DFAS website for a military W-2 - <a rel="nofollow" target="_blank" href="https://www.dfas.mil/militarymembers/taxinfo/taxstatements.html">https://www.dfas.mil/militarymembers/taxinfo/taxstatements.html</a>
DFAS makes W-2 forms available online. So before trying to use his LES to do taxes (a last resort), he should try to view and print his W-2 using the DFAS site: https://www.dfas.mil/militarymembers/taxinfo/taxstatements.html).
DFAS will want him to set up a MyPay account, if he doesn't already have one. See above link for instructions & link to MyPay.
Some basic LES boxes and their corresponding W-2 boxes:
Box 34 LES would correspond to box 1 of the W-2, box 38 corresponds to box 2 of the W-2, box 40 corresponds to box 3 W-2, box 41 corresponds to box 4 W-2, box 42 corresponds to box 5 W-2, and box 43 corresponds to box 6 W-2.
For state, box 44 corresponds to box 15 W-2, box 46 corresponds to box 16 W-2, box 49 corresponds to box 17 W-2.