[2][3] During World War I, Semyon was a Captain and fought alongside the 6th Siberian Corps, and then became part of the operational staff management of the Northern Front.

After the Russian Revolution in April 1918, Pugachov volunteered to join the Red Army,[4] and served in several Soviet military districts across the country.

His main task was to guide the development plan to expel and defeat the forces of the White Army from the North Caucasus.

In May 1924, he commanded the Red Banner Caucasian Army, and from 1925 to 1928, he served as replacement for the Chief of the RKKA and aided in certain reforms done by Mikhail Frunze from 1924-1925.

He admitted his guilt on 11 March; however, after a confrontation with Sergei Georgevich Bejanov the next day, he refused from readings presented earlier.