Bismil got his name etched as a prominent freedom fighter with his participation in the Mainpuri conspiracy of 1918. Bismil along with Genda Lal Dixit, a school teacher from Auraiya, organised youth from Etahwah, Mainpuri, Agra and Shahjahanpur districts to strengthen their organisations, ‘Matrivedi’ and ‘Shivaji Samiti’. He published a pamphlet titled ‘Deshwasiyon ke Naam’ and distributed it along with his poem ‘Mainpuri ki Pratigya’ on January 28, 1918. To collect funds for the parties, they looted government coffers.
His ideals of freedom struggle stood in stark contrast to that of Mahatma Gandhi and he would reportedly say “independence would not be achieved by means of non-violence”. After conflicting views and growing resentment with the Congress party, he formed the Hindustan Republic Association which soon had leaders like Bhagat Singh and Chandrashekhar Azad.
On August 9, 1925, Ram Prasad Bismil along with companions Ashfaqulla Khan and others executed the plan of looting the train at Kakori near Lucknow. After the revolutionaries stopped the 8-Down Saharanpur Lucknow passenger train at Kakori, Ashfaqullah Khan, Sachindra Bakshi, Rajendra Lahiri and Ram Prasad Bismil subdued the guard and looted cash meant for the treasury. Within a month of the attack, the angered colonial authorities arrested more than a dozen HRA members.After the trial in the so-called Kakori conspiracy, these four revolutionaries were sentenced to be hanged.