Uncertainty

You write that the king probably won't catch deserters. That may be true. But how much should they bet on it? If the kingdom is medieval/feudal:

• Feudal levies are raised when the king calls his dukes, the dukes call their barons, the barons call their knights, and the knights round up some hapless peasants.
• The peasants do not own their farms. They have a (possibly hereditary) right to live there as part of their feudal rights and duties. Deserting now could give their landlord an excuse to evict them, a year from now or a decade from now, whenever he finds the time to try the miscreant.
• The peasants might be unable to conceive a society without knights in charge. They will gripe about bad overlords, and fondly remember good ones, but the system stays.

How do the conscripts figure to go home? Through a war-ravaged country? Without supplies? Could they read a map, if they had one to start with?