On 19 December 1941, during the Second World War, in the city of Hong Kong, Osborn was the Sergeant-Major of his company, part of the Winnipeg Grenadiers.
Forced to retreat under heavy fire, Osborn single-handedly covered his troops until they joined the company and assisted stragglers to their new position.
Later, his company was cut off from the other Canadian troops and completely surrounded by the enemy under attack.
During an exchange of hand grenades, having closed in on the enemy, Osborn threw himself on a live grenade saving the lives of those nearby.
For his actions he was awarded the Victoria Cross.
Prior to the war, upon emigrating from England, he settled in the Wapella area.
At Hong Kong on the morning of the 19th December, 1941, a Company of the Winnipeg Grenadiers to which Company-Sergeant-Major Osborn belonged, became divided during an attack on Mount Butler, a hill rising steeply above sea level. A part of the Company led by Company-Sergeant-Major Osborn captured the hill at the point of the bayonet and held it for three hours when, owing to the superior numbers of the enemy and to fire from an unprotected flank, the position became untenable. Company-Sergeant-Major Osborn and a small group covered the withdrawal and when their turn came to fall back Osborn, single-handed, engaged the enemy while the remainder successfully joined the Company. Company-Sergeant-Major Osborn had to run the gauntlet of heavy rifle and machine gun fire. With no consideration for his own safety he assisted and directed stragglers to the new Company position, exposing himself to heavy enemy fire to cover their retirement. Wherever danger threatened he was there to encourage his men.
During the afternoon the Company was cut off from the Battalion and completely surrounded by the enemy who were able to approach to within grenade throwing distance of the slight depression which the Company were holding. Several enemy grenades were thrown which Company-Sergeant-Major Osborn picked up and threw back. The enemy threw a grenade which landed in a position where it was impossible to pick it up and return it in time. Shouting a warning to his comrades this gallant Warrant Officer threw himself on the grenade which exploded killing him instantly. His self-sacrifice undoubtedly saved the lives of many others.
Company-Sergeant-Major Osborn was an inspiring example to all throughout the defence which he assisted so magnificently in maintaining against an overwhelming enemy force for over eight and a half hours, and in his death he displayed the highest qualities of heroism and self-sacrifice.
London Gazette, no.37517, 2 April 1946