Unsoldierly

His desertion was condemned as an unsoldierly act of cowardice.

For which most unsouldierly & unworthy action […] he had this insuing Judgement pronounced against him […]

1718, Alexander Pope, The Iliad of Homer, London: Bernard Lintot, Volume 4, Observations on the Fourteenth Book, Verse 81, p. 131, He does not say, to shun the Battel, for that had been unsoldierly, but he softens the Phrase, and calls it, to shun Evil:

Maurice. What, an unarm’d man? A man that never wore a sword? A priest? It is unsoldierly! I say, ye shall not!

It is a miserable story. Even Yate, who saw it happen, betrays an unsoldierly sigh.

But as soon as the man in uniform gripped his pen and started writing, a change came over him. Sweat began to pour from his hair, from his widow’s peak down on to his forehead, and from the back of his head down into his collar. […] Such unsoldierly apprehension was not encouraging.

A few of them limped unsoldierly in deference to blistered feet.

[…] you, soldiers, that shift unsoldierly The weapons that should be upright, at attention, like stiff grass-blades: