Is the punishment for disobeying a legitimate and duly authorised order six years in military prison?

Unfortunately this young Army Lt has been badly advised.

The matter whether or not the invasion of Iraq was legal is moot.

This young officer has been ordered to Iraq with his unit to serve under the terms of a duly constituted United Nations Mandate and at the request of the duly elected Iraqi Government. There is nothing illegal for him to base his objections on.