Following the suppression of the uprising, he joined the Revolutionary Insurgent Army of Ukraine and became a leading member, spearheading the negotiations between the Makhnovists and the Bolsheviks until his arrest and execution by the Cheka.

[2] The uprising failed, largely due to the hesitancy with which they carried it out: treating captured Bolsheviks with mercy and refusing to march on the headquarters of the Central Committee.

[3] By the autumn of 1918, the left SRs had gained an influence in the Makhnovshchina, working closely together with the Makhnovists in their mutual fight against the White movement and desire for the establishment free soviets.

[3] Although Left SR influence had mostly waned by the time of the White movement's advance on Moscow, Popov quickly became a leading member of the insurgent staff and Makhno's personal assistant.

On 29 September, he held a phone call with the Chairman of the Ukrainian Cheka Vasiliy Mantsev, during which Popov spoke about the "revolutionary purity" of the Makhnovists and mentioned how they had hanged emissaries from South Russia.

Speaking to large crowds at a number of meetings and debates in the city, Popov proclaimed the necessity of restoring power to the free soviets and demanded the extension of autonomy to the Makhnovshchina.