Final answer:
Kolya was arrested for deserting, which means abandoning military duty or leaving without permission, even if he didn't intend to desert.
Step-by-step explanation:
In the context of the question, the term 'deserting' refers to the act of abandoning one's military duty or leaving the military without permission. In many military systems, including the Russian military during certain periods, desertion was considered a serious offense and was punishable by law. Even if Kolya did not intend to desert, the act of leaving without permission was likely enough to warrant his arrest.