The war beyond the familiar

Imagine going into your military's basic training, coming out of combat in the army only to realize that many of the technologies used in war will not work for the battlefield and many of the victims have little defense against both you and the enemy. Well, that what soldiers from many nations will face when becoming to first UN army force in human history in Dimension X; a place that many people have only have first so much as breathed in the air as a child before coming back with new creatures in the family. Only because of a 17-year-old boy and his connection to the 2 prime spirits of that universe. However, he can only bring and not guide as it would break something they were taught.