There are muslim soldiers in india who are also on border and on the Pakistan border they are also muslim soldiers so who gets martyred when they fires on each other between indian muslim soldier and pakistani muslim soldier
Residing in lands of disbelievers is a hot topic in Islam. Prophet advised migration to such Muslims.
I disavow every Muslim who resides among the mushrikeen.”
Narrated by Abu Dawood (2645) and at-Tirmidhi (1604). Classed as saheeh by al-Albaani in Irwa’ al-Ghaleel (5/29-30)
Secondly many scholars are against working for armies of mushrikeen/darl ul kufr. Since it involves fighting against Muslims and with those with whom Muslims have treaties example Pakistan having treaties with China.
Thirdly, if dar-ul - kufr doesn't have any wars with Muslims, some scholars say Muslims can gain knowledge of the strategies of kuffar by joining these armies.
Coming to the question Pakistan is not a Sharia governed Country. It's difficult to conclude whether Pakistani Muslims die as Martyrs on path of Allah. Definitely Indian Muslims do not die as Martyrs in path of Allah.
PS: I'm Indian by natural citizenship.
Only those are martyrs in Islam who were fighting in the cause of Allah, for the superiority of Islam.
It is difficult to reason how supporting India against Pakistan would be of any benefit to Islam, as it is a secular country with a polytheist majority. Pakistan is not fully Shariah compliant but it has at least a semblance of an Islamic identity.