POD: march 1921, although the soviets have been defeated at Poland in this TL, they are not suffered so far great losses than in OTL battle of Vistula that see the polish defeated the Red Army, this means that in the Peace of Riga the soviets recognises Poland and in great part his expansion into the east, at the difference of OTL because the soviets are with less casualties, the peace permits the soviets retain the region of Pinsk (more or less the region east of city of Kowno (that is in hands of Poland, in TTL a border city) the polish obtains also Galitzia Oriental and the zone of Vilnius.
This means that Trotsky has not loss so influence because the astounding defeat in OTL, this means that combined with other factors the X Party Congress of march 1921 sees some of the supporters of Trotsky reelected, a thing that not happen in OTL, in TTL Krestinsky, Preobrazensky and Serebryakob between others trotskysts were reelected.
Another POD that I use was a better health situation for Lenin, he is sick and ill, but in TTL better medician help and repose make possible to Lenin live until 1927, in this case it has importance, when in 1922 the question of the nationalities was presented in Soviet Union, Lenin adopted a policy of confronting the policy of centralization advented by Stalin and others, Lenin also send a letter to Trotsky indicating that he wanted that Trotsky and not Stalin assumed the defense of the Georgian nationality cause (IIRC about to let some kind of freedom to nationalities in this case Georgia) before the Central Committe, in OTL Trotsky refused, he has no sufficient base to confront Stalin and also saw Lenin as an ill and sick person that could die in any moment.
In TTL he accepts: with a better position in the Central Committee: roughly 40 % Trotskysts, 45 % Stalin or pro positions of Stalin ,but with the rest indecises, Trotsky takes the defense, he expects that the support of Lenin could give the votes of the indecisses, and ... yes he succeeds.
Lenin like in OTL distrusts Stalin (and also Trotsky although more Stalin than Trotsky) and also he not forgive that Stalin have made use of unpolite words with his wike Krupskaia.
After the success of Trotsky, Stalin begin to have some kind of fear, more because Lenin seems although sick could endure some more years and it is clear that Lenin is beginning to have some kind of many against Stalin.
Stalin knows that time is precious, before Trotsky and allies could strengthen his position in the Central Committee, because the recents political successes of Trotsky, the succesful defense of the Georgian nationalities, and after the support of Lenin as Trotsky as a defender of Lenin position to respect some kind of rights to nationalities.
When Lenin falls in a severe ill in 1924 (but no so severe than in OTL to make him fall die), Stalin thinks that is the moment, he gets a reunion of the Central Committee to talk about the health of Lenin (letting some indirects about the possible mental health of the father of the revolution) and also gets a reunion of the Communist Party in a Congress to discuss this inmediately, when the Congress meets, the positions between Trotsky field and Stalin field are more less equal but with a series of indecises that are not pro-Trotsky or pro-Stalin; Trotsky temper and his weak point: the arrogance and the fact that Stalin has showed clearly his skills of organization seemed but that could make Stalin the candidate elected by the Congress to assume provisionally powers while Lenin is on bed.
Stalin could smile, only that this time is not so easy like in OTL, he even with a situation more favourable for Trotsky is possibily capable to get the power, the fact but that Trotsky have better situation in the Communist Party than in OTL makes possible a lot of debate, even with this Stalin seems have the upper hand, narrowly, but definitevily the upper hand, it is then when a dramatic apparition shows helped by his wife and some other friends, an apparition that demands talk to the Congress: is Lenin.
For Stalin it is the defeat, the Lenin discourse is an authentic accusation to the fact that Stalin not showed respect to Lenin, his wife, the ideals of the Revolution, with the excuse of my illness, he searches only the power, and although Lenin no doubt in saying that Trotsky is not perfect, Stalin has showed also arrogance in his kind of attempt of legal coup.
The Congress votes, and is clear that Stalin proposition of give him provisional powers has failed, worse of all for Stalin is clear that Lenin hates him, fearing of the next movement, he decides to go to Georgia to have some of relax, in fact fleeing.
Trotsky is now supported by Lenin,and after pression from Lenin, Trotsky, Kerstinsky, Ovseyenko and other trotskysts and after Zinoviev and Kamenev decides that is better not support Stalin, it is demanded to Stalin to go from Georgia to Moscow to answer an investigation commission about his attitude.
Stalin refuses to go to Moscow, he fears that this could be the end of him even phisically, an try to rally any support that he could to oppose this measure of investigate him, is then when Frunze and a group of red soldiers under orders of Trotsky and Lenin appears to escort him until Moscow, it is no clear like in these kind of facts what truly happens then, it seems that Stalin tries to flee, in some moment seems that he shots (could be at the air, could be even not shot and is only a Frunze lie) but there was some firefight (Frunze says that some Stalin supporters or bodyguards opposed violenty also to the arrest) in any case in the attempt of flee Stalin is wounded and falls with so disfortune that he opportunely brokes his neck and dies

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