Is it permissible for a Muslim soldier to combine and shorten prayers when not in his hometown?

It is impermissible to acquire the citizenship of non-Muslim countries except out of dire necessity. If you are compelled to acquire citizenship and are forced into military service, then safeguard your prayer and hold fast to your religion, and pray each prayer at its appointed time. If the nature of the work prevents you from praying at its appointed time, or if the employer prevents you and you are compelled, then there is no harm in combining the Asr prayer with Dhuhr, and the Isha prayer with Maghrib, either by advancing or delaying them, without shortening them, provided there is hardship and difficulty. The Hanbali jurists permitted combining prayers while resident to alleviate hardship, and they cited as proof that the Prophet, peace and blessings be upon him, combined prayers when neither traveling nor raining, "intending not to cause hardship to his Ummah." However, if there is no hardship or difficulty, then combining prayers is not permissible. It is not permissible to delay a prayer beyond its appointed time except in cases of permitted combining, and combining is specific to the prayers that share a time: Dhuhr and Asr, and Maghrib and Isha.