Copying this post a user submitted on reddit.

Comrades I am sure you have seen this claim “Stalin adopted the Left Oppositions Super Industrialization plan” or something similar it shows up in Animal Farm, to more “serious” critiques from Left Communists and Anarchists. So I want to debunk this claim because i am tired of hearing it, but it unfortunately permeates a lot of western histories of the events.

The History

Let us start with a good primary source on this from a political opponent of both Trotsky and Stalin, Ryutin.

Ryutin was certainly on the party right, he was very against Collectivization and for very slow Industrialization. It is also worth noting this was written in 1932 and the fullest extent of Stalin’s push to industrialize and forced collectivization were still being carried out.

"Having robbed the thread of Trotsky and his group, Stalin affirms that his super industrialisation pressure is not only on the kulaks but also on the middle peasantry; extraordinary tax, extortion of one and a half milliard roubles from the cooperatives and in the future an increase in prices,—cards, queues—all theses are something quite other than suggestions of the Trotskyists.

Stalin, of course, led the economic platform of Trotsky to the limit of the absurd, to the logical end, but this was not accidental : “in for a penny, in for a pound”."

So he compares it to robbing a thread, or taking it to the very extreme. Now Ryutin felt there was similarities and without a doubt the Left Opposition was for Industrialization and Collectivization, and Stalin did implement these, but to such an extreme. The Left Opposition was for Voluntary Collectivization, and not industrialization at the pace Stalin called for, as well as they were not for the targeting of all peasants.

So as far as opinions from histories I want to start with Stephen F. Cohen Stalinism and Bolshevism an article from Robert C. Tucker’s Stalinism: Essays in Historical Interpretation

"Trotsky and the Left opposition are said to have been anti-NEP and embryonically Stalinist, the progenitors of "almost every major item in the political program that Stalin later carried out." Stalin is then having said to have stolen, or adapted, Trotsky's economic policies in 1929. Having portrayed a "basic affinity between Trotsky's plans and Stalin's actions," these secondary interpretations suggest at least a significant continuity between Stalinism and Bolshevik thinking in 1920's, and underlie the general interpretation of NEP. They are, however, factually incorrect."

"Even Preobrazhesnky, the avatar of "super-industralization" who's fearful arguments about the necessity of "primitive socialist accumulation" based on "exploiting" the peasant sector are often cited as Stalin's inspiration, accepted the hallmark of NEP economics. He wanted to "exploit" peasant agriculture through market relations by artificially fixing state industrial prices higher then agricultural prices. Both he and Trotsky, and the Bolshevik Left generally, thought in terms of peasant farming for the foreseeable future. However inconsistent their ideas may have been, neither ever advocated imposed collectivization, much less wholesale collectivization as a system of requisitioning or a solution to industrial backwardness"

"Trotsky's actual economic proposals in the 1920s were based on the NEP and its continuation. He urged greater attention to heavy industry and planning earlier than did Bukharin, and he worried more about the village "kulak"; but his remedies were moderate, market-orientated, or, as the expression went, "nepist." Like Bukharin, he was a "reformist" in economic policy, looking towards the evolution of NEP Russia towards industrialism and socialism. "

From Stephen F. Cohen’s Bukharin and the Bolshevik Revolution a Political Biography.

"The turbulent months between April 1929 when Bukharin was defeated and December were among the most important in Russian history. They brought three large, related events: an abrupt radicalization of Stalin's policies, accompanied by his emerging practice of making major decisions autocratically; a further worsening of the state's relations with the peasantry; and the onset of a furious official campaign against the Right opposition and Bukharin personally, which grew into a repudiation of political moderation generally. Together these developments led to policies unlike anything ever advocated by any Bolshevik group, including the Left, to the final destruction of NEP, and to the coming of Stalin's "revolution from above." p.329

Now from Moshe Lewin’s Political Undercurrents in Soviet Economic Debates

"In propaganda texts, the majority's spokesmen accused the Left of planning to liquidate the NEP, to oppress the peasantry, to raise prices and lower the standard of living, and other sins. But the latter, no doubt sincerely, reasserted that it favored the NEP, did not intend to expropriate the property of the kulaks, nor indeed, that of any other private entrepreneurs, and that it, in fact even, welcomed some growth of these elements provided the growth of the socialist sector, mainly industrial, was constantly assured. They opposed using the G.P.U. against the private sectors.p.35

From the same text we can take a look at historical opinions too to back this up.

“Trotsky, too in a brochure written in August 1925 developed positive expectations about long-term prospects of the NEP and defined it as “cooperation and competition” between socialism and capitalism. “ Preobrazhensky originally an opponent of the NEP in 1921 supported it and its transitional character and was against any violent elimination of it or forced collectivization."

Again from Moshe LEwin’s Poltical Undercurrents in Soviet Economic Debates.

"Trotsky could afford to endorse the NEP wholeheartedly because he too had some previous positions to call back on. He was , in fact, the first to have advocated NEP-like changes as early as Februrary 1920, but his proposals were then rejected by the Central committee. Trotsky then turned to his plan of etatization of the trade unions, but this too was rejected by Lenin, who was soon to adopt the NEP (on this both leaders agreed). For Trotsky's propsals of a new policy towards peasants"

Conclusion

Given Trotsky was one of the first to propose NEP like changes, and continued to defend it. How could one say that Stalin stole his economic position when Stalin got rid of the NEP. This is a very big difference in economic positions. Trotsky nor the LO ever advocated for forced collectivization, or getting rid of the NEP. Stalin’s position originates with him, not Trotsky, not the Left Opposition and certainly not Bukharin.