How can one make up for missed prayers due to a military mission, taking into account extreme fatigue and sleep?

It is not permissible to delay the prayer beyond its appointed time under the pretext of being busy. Rather, one must pray according to the circumstances, either with ablution (wudu) or dry ablution (tayammum (definition)), and if possible, combine the two prayers that share a common time. One must repent from this great sin, which is intentionally abandoning the prayer until its time has passed, and these prayers must be made up immediately.