Can we join the army in non-Muslim countries?

All praise be to Allah and may His peace and blessings be on His final and greatest messenger, Muhammad.

Although the Muslims may defend their homeland – including non-Muslim countries that grant them freedom of worship – against outside aggression, to protect their lives, properties and freedom of worship of their lord, they may not be part of any aggression (offensive) done against others. This includes working in a combatant or non-combatant capacity.

The wars conducted by the companions against the Persians and Romans and their likes were for the cause of Allah and that is the cause of justice, for He is The Infinitely Just. There is no doubt they defeated two tyrannical empires and brought their subjects the much yearned for security and justice. The historical accounts testify to this fact, and those who deny will not be able to block the light of the sun.

Moreover, the price of modern war is enormous; with loss of life and wealth that is hundreds of thousands of times more than the war during the time of the companions. This should make anyone entertaining non-defensive acts of war obliged to re-think their plans and alternatives hundreds of times.

Allah knows best.