Notice the time lag between the events of 1936 and the realization that the Soviets were “wag[ing] a war against the Anarchists.”
That's not correct. If the Comintern Parties[^note1] and their comissaries were waging a war into the anti-fascist forces, were against other communists: mostly against the POUM and troskist.
The POUM (Partit Obrer d'unificació Marxista / Workers Party of Marxist Unification), the group where George Orwell joined, was a non-troskist Marxist-Leninist Party, which wanted to do the revolution at the same time as overcoming fascism, i.e. the same strategy that the anarchists of the FAI (Federació Anarquista Ibèrica / Iberian Anarchist Federation) and CNT (Confederació Nacional del Treball / National Confederation of Labor).
The POUM was banned (accused of collaboration with fascism) and its leader Andreu Nin disappeared. Until the 90s, with the declassification of KGB documentation, it was not known what had happened to him: he was detained, tortured and murdered by the NKVD without having 'confessed' to any crime.
I do not deny that there was persecution against anarchists, but I do deny the degree of animosity towards them that anarchist historiography often presents. The greatest ideological "danger" of the Comintern, those against whom they showed the greatest animosity within the anti-fascist bloc, were not the anarchists, nor the majority socialist party, nor the petty-bourgeois parties... they were other communists who do not share their positions.
[^note1]: PCE (Partit Comunista d'Espanya / Communist Party of Spain) and PSUC (Partit Socialista Unificat de Catalunya / Unified Socialist Party of Catalonia).