Peace cricketplaya
Iconoclast answered the query. The reason why Muslims join non-Muslim armies is because every soldier of any army joins it for a handful of given reasons. Some extra reasons may be because, they couldn’t find other jobs, or because their friends have joined. The fact that they are Muslim pre-supposes that every Muslim inherently knows what ‘responsibility’ they have as Muslim is.
In fact joining any army today is unIslamic, because they all operate in accordance with principles that go against the principles of righteous conduct and compassion. Muslims must only fight out of compassion and by doing so elevating the name of Islam. As Muslims it is our right and duty to protect our homes and communities and ourselves and families and to protect the name of Islam, from those who want to destroy any of these things. This can be done without joining any army. It is entirely possible for someone to join an army and be asked to kill Muslims, even joining Muslim armies leads to this, but this is no worse than killing any innocent human beings, destroying trees, infrastructure, animals and the environment. Wars and battles didn’t involve destruction of the mother Earth in the past. Today modern warfare involves destruction. None of this is Islamic. We have far greater things to worry about perhaps the real reason why Muslims fight in ‘kuffar’ armies is because you and I have not done our jobs to show humanity what it means to be Asraf-Al-Makhluqaat.
We can’t ask that question without first blaming ourselves for being ineffective at being true messege relayers of the Light of Islam.
So, this means, it is unIslamic to join the Pakistani army, the saudi army, the lebanese army, the jordanian army, the iraqi army (wait, do they even have one anymore??) and the irani army?
I’m also supposing that you believe it’s wrong to join any extremist group that uses warfare or weapons to get its point across, including the people who laid seige to Lal Masjid.