Edgar Thomas Conley successfully completed his studies at West Point, where he earned the lifetime nickname of "Sheriff" for mediating a fight between cadets, and did well both academically and in extracurricular activities. Conley graduated and was commissioned a 2nd Lieutenant of Infantry on 11 June 1887. After a brief stint with the US 15th Infantry in the New Mexico Territory, newly promoted 1st Lieutenant Conley was assigned to Company G, 21st Infantry on 1 February 1898. The 21st Infantry was deployed for service in the Spanish-American War, landing on Cuba with the Fifth Army Corps in late June 1898. On 1 July 1898, the 21st Infantry took part in the assault on San Juan Hill outside Santiago, Cuba. Lieutenant Conley was cited for gallantry in the battle, making him eligible to wear the Silver Star Medal when it was approved in 1932.