Before World War I, he served as a patrolman for the horse breeder Korolkov, after he entered the service in the equestrian artillery, where he rose to the rank of sergeant.

In June 1919, Maslakov was appointed commander of the 1st separate brigade of the 4th cavalry division for his skillful leadership of the regiment and for his "displayed energy in military affairs".

In early 1920, Grigory Maslakov assumed command of the 14th Maikop Cavalry Division and in the same year became a member of the Russian Communist Party (Bolshevik).

For his refusal to carry out punitive actions against the rebels in early February 1921, a counter-revolution case was initiated against Maslakov with the aim of bringing him to trial by a revolutionary tribunal.

On February 11, 1921, Maslakov was outlawed, since “on the basis of drunkenness and demagoguery,” he dragged a significant part of the soldiers of the 19th cavalry regiment into mutiny and “betrayed the cause of the revolution,” as the order said.

On March 10, 1921, Maslakov and Brova with their detachments, with the consent of Nestor Makhno, moved to the North Caucasus, receiving the name "Caucasian Insurgent Army of the Makhnovists".