Bryant Gustavus Symes was born on the 13th March 1900 at Weymouth, Dorset. Son of Gustavus Phelps Symes (army Colonel of Volunteer Soldiers) and Jessie Hetley Symes (née Betts).
Bryant Gustavus Symes was educated at the Royal Military College, Sandhurst.
He was commissioned into The Dorsetshire Regiment (emergency commission) on the 14th July 1921 with the rank of 2nd Lieutenant. He was promoted to Lieutenant on the 14th July 1923.
In 1931 (March) he served with the 1st Battalion The Dorset Regiment at Chakrata, India. In June 1933 they moved to Sialkot.
Promoted to Captain on the 1st September 1936.
By January 1937, still serving with the 1st Battalion The Dorset Regiment he was now at Landi Kotal the highest point on the Khyber Pass and is the route across the mountains to the city of Peshawaron on the Afghanistan border.
He was promoted to Major on the 1st August 1938.
In January 1939 he joined the 2nd Battalion The Dorset Regiment at Aldershot.
The 2nd Battalion The Dorset Regiment joined the British Expeditionary Force and were sent to France and Belgium, where they remained until they were drive back to Dunkirk by the advancing German forces in May 1940.
He was awarded the O.B.E. for distinguished service in the field (London Gazette 11th July 1940).