What should one who has had a wet dream during a military course and is prevented from performing ghusl, being allowed only to perform wudu before Fajr prayer and training, do?

If the organizers of the course permit ghusl (definition) (ritual bathing), then there is no harm in joining it. However, if they prohibit it, then if you are able not to join it, do not join it, due to the neglect of obligatory duties involved. But if you are compelled to join it, then you must maintain ritual purity and pray on time. If you are prevented from ghusl or wudu (ablution), then perform tayammum (definition) (dry ablution). If you are prevented from tayammum, then pray in your current state. Pray in your training place if you are prevented from the mosque. You must also report the matter to the competent authorities.