Desmond, who hails from the nation's capital, Washington, DC, played collegiate soccer at the University of Maryland from 1982 to 1986, serving as team captain. He was named to the All-ACC Team in 1984 and 1985 and was later named as one of the ACC 50 Greatest Soccer Players All-Time.

In 1986 he was selected third overall draft pick and first draft pick for the Cleveland Force of the Major Indoor Soccer League (M.I.S.L.), the only professional soccer league in the country at that time. Armstrong went on to become an M.I.S.L. All-Star Team in his second season as a professional.

Desmond was named to the 1988 US Olympic Soccer Team, which competed in Seoul, Korea, where the US was knocked out of the competition by the eventual Gold Medal winners, the Soviet Union. Following the Olympics, he was then selected to represent the US in the 1990 World Cup held in Italy. It was the first time the US had qualified for the World Cup in 40 years and served as the spark that has driven the growth of the game in the US since their appearance. He won the inaugural Gold Cup with the US National Team in 1991 defeating Mexico in the semi-finals and Honduras in the finals.

Desmond then signed for Santos FC becoming the first American player ever to play professionally in Brazil. As a mainstay of the US team from 1987 - 1994, he transitioned from player to broadcaster being hired by ABC Sports during the 1994 World Cup in America as a studio analyst. He went on to work for ABC and Fox Sports as both a studio analyst and color commentator until 1998.

Desmond Armstrong served on the US Soccer Board of Directors from 1991 - 1994.

He acquired his US Soccer "A" Coaching License and became the National Director of Coaching for Soccer in The Streets from 1993 - 1998. In 2001, Armstrong was named Director of Soccer and Head Men's Coach of Montreat College, a small NAIA school nestled in the Mountains of Asheville, North Carolina.

He served on the United Soccer Coaches (formerly NSCAA) Board of Directors as President of the Black Soccer Coaches Committee from 2000 - 2002.

In 2004 Desmond created Heroes SC (now merged with Albion SC Nashville) with the intent of producing young professional American players who could go on to represent their country. Armstrong served on the coaching staff of US Club Soccer id2 between 2000 - 2003. He served as a Generation Adidas (formerly Adidas ESP) staff coach for four years having won both its Championship and All-Star Game. Desmond was named Chief Scout of Premier Soccer Academies (PSA) between 2003 - 2008. He scouted and coached future US National Team/MLS players (Wil Trapp, Columbus Crew, InterMiami FC, Minnesota United; Romain Gall, Columbus Crew, NYCFC, Malmo FF, Rot-Weib Erfurt). Other notable players that he has worked with include Charles Renken - Hoffenhiem, Seattle Sounders, Aslinn Rodas - Guatemala National Team, Carlos Salcedo - Mexican National Team, Matt Dunn, Ebby Perez, Andy Lubahn, and Kainoa Bailey . Following his time with PSA, Desmond worked with several MLS Academies as an Academy Coach. The list of clubs include the Columbus Crew, DC United (Winning the MLS SUM Cup in 2009) and Sporting KC where he was named Technical Director of Academy Affiliates and Academy Scout from 2014 - 2017.

Following his time at Sporting KC, Armstrong was named FISK University Director of Soccer operations and Head Men's Soccer Coach in 2017 - 2020. He went on to form AFC 615, which competed in the UPSL 2020 - 2021 before forming the Pioneer Premier League (PPL). The purpose behind AFC 615 and conversely the PPL, was for the furtherance of Desmond's commitment to developing young American players for the pros. Ezra Armstrong (Pittsburgh Riverhounds, USL Championship; St. Louis City 2, MLSNEXTPRO; NCFC USL Championship) and Dida Armstrong (St Louis City 2, MLSNEXTPRO), his two sons, exemplify his ability to carry talent to the pros.

TSX, a consultancy firm, was formulated in 2022 with the express purpose of utilizing Armstrong's extensive connections and experience throughout the Soccer community.