Osborne is Stanhope’s second in command. His loyalty - despite Stanhope’s flaws - remains throughout.
He makes it clear to the audience that Stanhope is an exceptional soldier.
When Hardy is gossiping about Stanhope, Osborne states "I love that fellow. I'd go to hell with him.”
While he recognises Stanhope’s flaws, Osborne understands that dealing with the horrors of war have made him the way he is. Because of this, he refuses to criticise Stanhope.
Osborne’s respected place in the company is shown in how Stanhope and the others call him "Uncle". We find out that he has been a schoolmaster and the other men - including Stanhope - look up to him.
After his death, Stanhope shows a softer side when he laments that Osborne was, “The one man I could trust - my best friend - the one man I could talk to as man to man - who understood everything”.
This is high praise coming from a commanding officer as heroic as Stanhope.
In the opening scene of the play Osborne is contrasted favourably with Hardy. For example, Osborne’s humour is less rude so we come to like him immediately.
He is kind and friendly to everyone he meets.
The fact that he has played rugby for England - but only mentions it to Raleigh in passing and asks him not to “breeze it about” - shows he is a humble man.
He is concerned for those around him, saying to Stanhope, “Now come and lie down. You’ve had a hard day of it.” He is the most popular officer with all the other men and is much lamented by Stanhope when he dies.
Given Osborne’s age he wouldn't have been recruited, he would have volunteered. This would have increased a 1928 audience's respect for him, showing his bravery in giving his life for his country.
We know he is terrified at the thought of being part of the raid. We see him reading from Alice's Adventures in Wonderland - he comforts himself with this childhood book and uses it as a distraction from the horrors of the war.
He accepts his fate with an “Oh” when he is told he will be involved and right up to the end - despite his fear - he does his duty bravely.