Every person subject to this Act who, not being in command of any of Her Majesty's ships, vessels, aircraft or naval establishments, fails when ordered to prepare for action by or against the enemy, or during any such action, to use his utmost exertions to carry the lawful orders of his superior officers into execution shall be liable, if the offence is committed with intent to assist the enemy, to death or any less punishment authorised by this Act, and in any other case, to imprisonment for any term or any less punishment so authorised.