the Fatwa Department Research Committee - chaired by Sheikh `Abd al-Wahhâb al-Turayrî
If joining the military service will prevent you from prayers or compel you to constantly delay your prayers until the time has passed, then you may not voluntarily join the military. The same can be said if joining the military will require from you engaging in sinful, immoral acts.
Otherwise, you may join the military service.
Source: Islam Today