Original sentence: As a member of the Independent Labour Party, he joined the militia of its sister party in Spain, the non-Stalinist far-left POUM (Workers' Party of Marxist Unification), in which he fought as an infantryman.He also depicted what he saw as the betrayal of that workers' revolution in Spain by the Spanish Communist Party, abetted by the Soviet Union, after its militia attacked the anarchists and the POUM in Barcelona in May 1937.He and his wife Eileen left Spain after narrowly missing being arrested when the  communists moved to suppress the POUM in June 1937.Soon after the outbreak of the Spanish Civil War, Orwell volunteered to fight for the Republicans against Franco's Nationalist uprising
Edited sentence: A member of the Independent Labour Party, Orwell felt impelled to fight as an infantryman in the anti-Fascist POUM (Workers' Party of Marxist Unification) during the Spanish Civil War.He also depicted what he believed was the betrayal of that workers' revolution in Spain by the Spanish Communist Party, which was abetted by the Soviet Union