Joining Zuhr and ‘Asr because of military manoeuvres
Question

                We are working in the military, and we often have to perform some military maneuvers, only for training. Since these maneuvers are just like a real battle, in terms of using real weapons and other military tactics, like having a zero hour which is the time set for the start of a military operation. The soldiers at zero hour should take their positions according to the plan, whether on the ground or inside the military vehicles. After this no one is allowed to leave his position under any condition, just like a real war. During the operation we fire by real weapons like if we were in front of a real enemy. These operations sometimes take the time of one obligatory prayer or two, sometimes even more than this. The problem we face is that we cannot pray on time in congregation. For example, an operation starts at 11.00 until before sunset. This takes time for both Dhuhr and ‘Asr, and no one is allowed to leave to pray every prayer on time. The question here is: is it permissible in this case to pray Dhuhr and ‘Asr together? Knowing that leaving the operation for every prayer will mean achieving a lower grade for the training.
Praise be to Allah.
    It is permissible to join Zuhr and ‘Asr at the time of the 
    earlier or later prayer in cases such as this, because joining prayers is a 
    concession that is granted. So whenever one needs to join them, one may join 
    them. Hence it is proven in al-Saheeh from Ibn ‘Abbaas (may Allaah be 
    pleased with him) that the Prophet  (peace and blessings of Allaah be 
    upon him) joined prayers in Madeenah at times 
    other than times of fear or rain. It was said to Ibn ‘Abbaas: Why did he do 
    that? He said: So that his ummah would not be faced with hardship., 
    i.e., that they should not suffer hardship because of offering each prayer 
    on time. End quote from Fataawa Noor ‘ala al-Darb by Shaykh Ibn 
    ‘Uthaymeen (may Allaah have mercy on him). 

    You have to advise those who are in charge of these 
    manoeuvres to choose times for them that do not conflict with the prayer, so 
    that the soldiers can join Zuhr and ‘Asr at the time of either the earlier 
    or later prayer. 

    May Allaah be pleased with ‘Umar ibn al-Khattaab, who wrote 
    to his governors in the regions: The most important of your affairs in my 
    view is the prayer. Whoever prays regularly has protected his religious 
    commitment, but whoever is careless about it will be more careless about 
    other things. Narrated by Maalik in al-Muwatta’ (6). 

    And Allaah knows best.