All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
If it is difficult for your brother to fast or if fasting may harm him because of that illness, it is permissible for him to break his fasting, and he must make up for the missed days when the reason for not fasting is removed. Allaah The Almighty Says (what means): {So whoever among you is ill or on a journey [during them] - then an equal number of days [are to be made up].}[Quran 2:184]
It should be noted that working in the military field in such countries involves many harms, some of which have been mentioned in Fatwa 85727. In that Fatwa, we clarified that it is not permissible for the Muslim to join this work. So, your brother must leave this job. If he insisted on keeping it, violating the prohibition – which is inappropriate for a Muslim – then let us discuss the issue of the meat you asked about:
If the case is as has been mentioned that there is no lawful meat because the animals are slaughtered by the unbelievers, not People of the Book, or slaughtered by People of the Book but not according to the correct Islamic manner, it will not be permissible for him to eat from it. This meat is considered meat of dead animals that Allaah The Almighty prohibited the Muslim from eating except under necessity. Allaah The Almighty Says (what means): {He Has only Forbidden to you dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allaah. But whoever is forced [by necessity], neither desiring [it] nor transgressing [its limit], there is no sin upon him.}[Quran 2:173] We do not think that your brother is under necessity to eat from that meat, because it seems that there is other food which does not contain this meat.
Supposing that he is forced to eat from this meat because he fears death if he does not eat from it, then it will be permissible for him to eat from it according to the necessity only. For further information, see Fataawa 84072 and 86821.
Allaah Knows best.