Arana became a member of this plot only in its later stages; the plot was initially led by Jacobo Árbenz and Aldana Sandoval. However, as the commander of the Guardia de Honor, Arana was in a position of substantial authority within the army. Sandoval was able to persuade Arana to join the coup in its final stages. On 19 October, Arana and Árbenz launched a coup against the government of Ponce Vaides. They were joined the next day by other factions of the army and the civilian population. Initially, the battle went against the revolutionaries, but after an appeal for support their ranks were swelled by unionists and students, and they eventually subdued the police and army factions loyal to Ponce Vaides. On 20 October, the next day, Ponce Vaides surrendered unconditionally. Both Arana and Arbenz fought with distinction in the coup. Arana, Árbenz and Jorge Toriello became members of a new three-person ruling junta, with Arana, who as a Major was the ranking army officer, becoming its senior member.