Nelson Margetts graduated from the mounted services school in 1909 and his military career advanced to his being appointed, in 1918, as a colonel of field artillery after having served in 1916-17 as aide-de-camp to General John Pershing. He served in the Inspectors General Department from 1927-29 and was granted an honorable discharge from the army in 1930. Margetts had a long polo career and won tournaments in his home country as well as in the Far East and in 1920, shortly before he won the Olympic bronze medal at Antwerp, captaining the US team, he was on the American Army side that beat Foxhunters at Ranelagh to win the Novices Cup.