My impression of the Great Purge is that most of what the people "confessed" to with regard to Trotsky was mostly bogus; Trotsky had no contact with these people, and he had no network of spies and saboteurs in the Soviet Union. HOI4 plays this a little differently, obviously. I was just wondering, did Trotsky actually have a base of support in the Soviet Union, and how likely or not is it that he would have been able to overthrow Stalin?
There certainly was no Trotskyite plot in the sense in which the Stalinists claimed, with wreckers, terrorists and so on. All of such claims by the accused during the show trials were forced out of them, which is amply documented, and are anyway absurd on their face.
Trotsky was understandably not forthcoming about the fact that in 1932 he did try to join the opposition bloc in the USSR and did maintain some ties to the Trotskyists there.
The documents establishing this were found by the researchers of the Institut Léon Trotsky and published by Pierre Broué in 1980. These are: 1. a letter from Trotsky's secretary Van Heijenoort to Trotsky's son Leon Sedov, 3 July 1937, about finding a copy of Trotsky's letter to Sedov about the bloc in an archive 2. the letter from Trotsky to Sedov found by VH in which Trotsky writes that "the proposal for a bloc seems to me to be completely acceptable." 3. a letter from Sedov to Trotsky written in invisible ink in which Sedov explains the composition of the bloc ("it includes the Zinovievists, the Sten–Lominadze Group and the Trotskyists (former “...”). The Safar–Tarkhan Group have not yet formally entered they have too extreme a position; they will enter very soon. The declaration of Z. and K. on the very grave mistake which they made in 1927 was made at the time of the negotiations with our people about the bloc, just before Z. and K. were deported" etc.).
This information is of course misused by the neo-Stalinists to claim that there was a real Trotskyist conspiracy in the USSR and this vindicates Stalin. But one needs just to read the documents in question to see that they actually refute the whole grand conspiracy claims.
Nothing in the documents confirms the charges of terrorism, espionage, wreckership, poisonings etc. The very Trotsky letter that proved the "bloc's" existence is simply damning to the Stalinist nonsense:
The proposal for a bloc seems to me to be completely acceptable. I must make quite clear that we are dealing with a bloc and not a fusion....How is the bloc going to express itself? For the moment, principally by the exchange of information. The allies keep us informed about what concerns the Soviet Union, as we do for them about what concerns the Communist International. We should agree on very precise arrangements for correspondence.The allies must send us correspondence for the Bulletin. The editors of the Bulletin undertake to publish the documents of the allies. But it reserves the right to comment freely upon them....The bloc does not exclude mutual criticism. Any propaganda by the allies on behalf of the capitulators (Grünstein, etc.) will be inexorably, mercilessly resisted by us.
We see a tentative testing of the waters by an outcast, not a grand terrorist plot. The intended bloc (consisting of numerous factions, not a monolithic entity and certainly not under Trotsky's control) was short-lived - most of its leaders soon got arrested. Indeed, Sedov himself mentions such an arrest in his letter.
Did Trotsky want to return? Sure. But he was unimaginably far from his goal.
The information about the bloc, however, eventually morphed into the overarching "Trotskyist plot" during the thoroughly staged Moscow trials.