See my post "Kuchak Khan and the Gilan Soviet Republic" at
https://www.alternatehistory.com/forum/threads/kuchak-khan-and-the-gilan-soviet-republic.339145/:
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... (1) What if Kuchak Khan, with Soviet support, and still having a united front with the Persian Communists, had moved against Teheran in the summer of 1920 (instead of doing so as a desperation move after the Soviet-Persian treaty of 1921)? At that point, British prestige in Persia was at a low ebb, and there was no strong leadership in Teheran (Reza Khan had not yet taken control of the Persian Cossack Brigade, let alone of the Persian government. [1]) Carr thinks that "Had the Soviet Government been able to press home its advantage, it might have established its authority in Teheran in the summer of 1920. But its power was not yet great enough, *especially with its current preoccupations in Europe*, for decisive action." (p. 246; emphasis aded) So while I have in the past been skeptical of claims that Pilsudski saved western Europe, maybe he did save Persia?... (And not just from the Soviets, since a pro-Soviet regime in northern Iran would be an inducement for the British to stay in southern Iran.)
(2) Was a long-lasting united front between Kuchak Khan and the Persian Communists possible if they hadn't blown everything by openly stating their intentions? It is of course certainly possible that Kuchak Khan would--especially if he did manage to seize Teheran--have "done a Chiang Kai-shek" and broken with the Soviets and the Persian Communists regardless of what the latter two would have done. Yet we should remember that at least two groups have had an interest in downplaying Kuchak Khan's 1920 radicalism, "soviet" rhetoric, and ties with Moscow. The first is Soviet historians, in order to justify Moscow's subsequent abandonment of Kuchak Khan. The second is post-1979 Iranian historians; Kuchak Khan became a hero in the Islamic Republic, being regarded as one of the first martyrs to what would become the Pahlevi dynasty. Obviously, it was convenient to minimize such a man's alliance with the atheistic Bolsheviks.
(3) Given Stalin's support for Kuchak Khan, is there any way (in the event of Lenin dying or being incapacitated earlier than in OTL) Stalin could have come to power earlier, if not yet as a sole dictator, at least as a sufficiently powerful oligarch to save the Gilan Republic? (Note that Stalin for some time to come would not entirely give up the possiblity of supporting "autonomous" regimes in northern Iran, as the Kurdish and Azerbaijan republics of the 1940's would show...) Even if the other party leaders did not share his obsession, perhaps they would not be interested enough to come out against him and support Rothstein, as Lenin evidently did?
(4) What would the reaction from foreign nations--notably Turkey and Great Britian--have been? I think the Kemalists would welcome a Kuchak Khan/Soviet victory. At this point Kemal was very pro-Soviet (which of course was quite compatible with suppressing Communists within Turkey) and anti-British, and Kuchak Khan's record had been anti-British and pro-Turkish. Remember that Kemal made no objection to the Soviet conquest of the three Transcaucasian republics, including Azerbaijan, which was ethnically Turkish. "Kemal and his emissaries assured the government of Soviet Russia that they shared none of the Panturanian ambitions of the Young Turks who had ruled the Ottoman Empire during the war, and had given up all claim to the North Caucasus and Azerbaijan." Richard Pipes, *The Creation of the Soviet Union,* (Harvard UP 1964), p. 222
Now it is true that Transcaucasia had been Russian before 1917. But northern Persia had after all been recognized as a Russian sphere of influence by the Anglo-Russian agreement of 1907. If Kuchak Khan would attempt to take over not just Teheran but all Persia, I suppose that even Lloyd George, who favored a less aggressive Persian policy than Curzon, would object, but I am not certain what he would do. At the very least, there could be an attempt to detach Khuzistan and other oil-rich parts of the south from Persia. Actually, the British attempted to do this even with Reza Khan in OTL:
"[On becoming prime minister in 1923] Reza Khan also retained his post as minister of war and continued his efforts to suppress the tribes and rebellious elements in Kurdistan, Azerbaijan, Fars, Mazandaran, Luristan, Gorgan. Khorasan, and Baluchistan. None of these campaigns was easy, but the riskiest move by far was the decision in 1924 to attack Sheikh Khazal of Mohammareh in Khuzistan (then called Arabistan). It was rumored that Ahmad Shah was inciting Sheikh Khazal in order to make trouble for Reza Khan, and the British certainly regarded him as a key protege in the web of petty emirates they had created around their interests in the Persian Gulf. Khazal had refused to pay taxes, written the Majles to complain that Reza Khan was a menace to the shah, and plotted to have Khuzistan incorporated as part of the British mandate in Iraq; Britain warned Reza Khan against intervening and sent gunships to the area. Unintimidated, Reza Khan caled the bluff and marched on Mohammareh in person. In the end, the British were more concerned about damage to their oil installations than Sheikh Khazal's autonomy and did nothing to defend him. He quickly surrendered and was later arrested and sent into a comfortable exile in Tehran. Probably no other event so enhanced Reza Khan's reputation as his willingness to confront the British lion in one of its chief lairs." Elton L. Daniel,*The History of Iran* (Greenwood Press, second edition 2012), pp. 135-6.
https://books.google.com/books?id=mri93AaexX8C&pg=PA135
With Reza Khan, the British were just bluffing; with Kuchak Khan, given his anti-British, pro-Turkish, pro-German, and pro-Bolshevik past (even if he were to break with the Bolsheviks), they might actually insist on the separation of Khuzistan and use force to accomplish it. It could then become the same target for Iranian irridentists that Kuwait would be for Iraqis...
[1] I am not certain how efficiently the Cossack Brigade would have fought against Kuchak Khan before Reza Khan took control of it. Reza's son, Mohammed Reza Shah Pahlevi, was later to write that "At the beginning of 1920, Russian officers still commanded the Persian Cossack Brigade. They were nominally all White Russians, but some of them had sold out to the Bolsheviks. When the brigade went into action against Red Russian units which had invaded northern Persia, the Bolshevik officers were guilty of outright treachery to us. My father's nationalism convinced him that he must get rid of all Russians in the brigade. In August of 1920, my father acted as his conscience required. He engineered the dimsissal of the Russians in the brigade and he himself became commander." *Mission for My Country*, p. 38. Obviously, the late Shah is not being entirely objective in trying to justify his father's grab for power, but the Cossack Brigade does not seem to have resisted the Bolshevik incursion of 1920 very strongly...