Any person subject to this Act who commits any of the following offences, that is to say,--
         (a) when in command of a guard, piquet, patrol or post, releases without proper authority, whether wilfully or without reasonable excuse, any person committed to his charge or refuses to receive any prisoner or person so committed ; or
         (b) wilfully or without reasonable excuse allows to escape any person who is committed to his charge or whom it is his duty to keep on guard;
shall, on conviction by court-martial, be liable, if he has acted, willfully, to suffer imprisonment for a term which may extend to fourteen years or such less punishment as is in this Act mentioned; and if he has not acted willfully, to suffer imprisonment for a term which may extend to two years or such less punishment as is in this Act mentioned.