He previously served as the deputy chief of space operations for strategy, plans, programs, and requirements.

Garrant received his commission from the Air Force Reserve Officer Training Corps program at the Johns Hopkins University in 1991.

[3] His first assignment was as systems engineer and program manager at the National Security Agency's Document and Data Networks Division for three years in Fort Meade, Maryland.

He served two years in that position until he was assigned as executive officer to the director of air and space operations of USAFE.

After that he deployed to Kabul, Afghanistan, and Al Udeid Air Base, Qatar, from October 2013 to April 2014 as deputy director for regional teams for operational contract support and chief of audit readiness in support of the Afghanistan war.

In 2019, he was assigned to the Missile Defense Agency (MDA) at Redstone Arsenal, Alabama, as the program executive for ground-based weapon systems.

[5][3] In April 2021, while assigned at the MDA, Garrant was nominated for transfer into the United States Space Force.

[6] In June 2022, Garrant was nominated for promotion to lieutenant general and appointment as the deputy chief of space operations for strategy, plans, programs, and requirements.

He would replace Lieutenant General Michael Guetlein who was selected to serve as vice chief of space operations.

[11][12] His nomination were among the hundreds of military promotions held by Senator Tommy Tuberville in opposition of the Department of Defense's abortion policy.