Can anyone help find 'A.O' ?

Richard Webster asks if anyone has any information concerning a First World War soldier poet who published his work using the pen name A.O?  His surname was Osborne and he was possibly a Major with the 4th Irish Dragoon Guards, who formed part of the British Expeditionary Force. He may have served throughout the war and survived it.

Richard surmises from his poems that he might have been public/grammar school educated, possibly classics?

This is one of A.O's poems posted by Richard on the War Poets Association Facebook Page:

THE NIGHT ATTACK

Hark ! The still night
rebellious voices wakes
In midnight
chorus from the groaning hills,
And all the
vales of Aisne and Vendresse
Echo reverberant
to the fiery hate.
Rises the loud
refrain, crescendent roar,
Percussion, re-percussion,
ceaseless strife.
Relentless
onward comes the march of death
Quick-pulsing
thunder of the loud barrage.
A.O.

I have looked in my copy of Catherine W. Reilly's "Bibliography of English Poetry of the First World War" and can't find anything there for Richard.  All help greatly appreciated.  Many thanks.