Is it permissible for me to shorten and combine prayers, given that I am a civilian accompanying military forces in a war zone, especially since the mosque in the encampment combines prayers?

A Muslim must perform the prayer at its prescribed time. However, if there is difficulty and hardship in doing so, it is permissible to combine two prayers, provided that the hardship justifying the combination is certain or highly probable. If you are a traveler and do not intend to stay four days at your destination, it is permissible for you to combine and shorten the prayers.