There are some cases that we can pick as examples, those examples are: Doctor/patient confidentiality brings up both loyalty (confidence) and honesty (truthful diagnoses, revelations of illness, etc.). Attorney/client privilege brings this up. Does a lawyer's loyalty to her client require her to be dishonest in the courtroom? Does a lawyer's requirement to be honest in the courtroom require her to be disloyal to her client? Parent/child protection is another. Do some of the lies that parents sometimes tell their children constitute (in part) loyalty? Does demonstrating familial solidarity excuse not being completely honest? Should a prisoner of war remain loyal to his country or be honest in an interrogation?
In the lawyer-client case, that "loyalty" is explicit in a contract (they supposedly can’t do/say anything that would incriminate their client), so they are kind of excused for being untruthful.
In the parent-child case they don’t mean to perpetuate that lie, just to postpone the truth until the kid is mature enough to understand it because they believe that it would be detrimental to them knowing the truth before that (this rests in such belief, if they knew that its not bad for them to know it, they would tell them the truth).
The soldier should have considered the possibility of that happening when he promised loyalty, if he was honest in the first place then there is no conflict and he will stay loyal, if not, I think it will goes to the other side. We know that for soldiers they have to obey and serve their country. We have the term “right or wrong is my country” and we will apply it in all situation.
Based on the examples above, we still face a cross opinion regarding loyalty and truth. But, personally I will choose loyalty above everything because truth is something that can be manipulated but when you are loyal I think it is going to be last forever.