structural:reformatting, structural:summarization
Historical reputation

In modern historiography, Trotsky's legacy has evoked a range of conflicting and diverse views. Biographer Paul Le Blanc stated "for millions of people throughout the world, Trotsky was initially seen as a revolutionary liberator ". He was viewed by contemporaries in the initial Soviet period and later historians as the hero of the revolution. Bolshevik figures such as Anatoly Lunacharsky, Moisei Uritsky and Dmitry Manuilsky agreed that Lenin’s influence on the Bolshevik party was decisive but the October insurrection was carried out according to Trotsky’s, not to Lenin’s, plan. Historian Betrand Patenaunde also noted his social appeal among the Petrograd workers in which he drew "vast crowds of workers, soldiers and sailors in Petrograd with his spellbinding oratory in 1917".

In the Soviet Union, his reputation gradually deteriorated over the course of the succession struggle as his views were presented as sectarian and anti-Leninist. Throughout the Stalin era, his name and image would be erased from history books, museums and films. At the same time, Trotsky became a convenient bogeyman for Soviet affairs and was associated with ideological heresy. The works of Trotsky also remained banned until the Gorbachev era. Following the de-Stalinization period, later generations of Soviet and Russian historians would reevaluate his role in the history of the revolution with varying interpretations.

Scholarly consensus holds Trotsky to have demonstrated remarkable leadership of the Red Army during the Civil War. He had been awarded the Order of the Red Banner for his role in the Red Army such as organising the defence of Petrograd when other members of the Bolshevik leadership were prepared to abandon the former capital. According to military scholar, William C. Martel, scholars view Trotsky as "one of the outstanding figures in modern military history " and a "directing genius ". Swain asserted that the Bolsheviks would certainly have lost the Civil War within a single year without Trotsky as leader of the Red Army.

A number of scholars and Western socialists have argued that Trotsky represented a more democratic alternative to Stalin with particular emphasis drawn to his activities in the pre-Civil War period and as leader of the Left Opposition. Prior to the October Revolution, Trotsky had been part of an old radical democracy which included both Left Mensheviks and Left Bolsheviks. He had also proposed the election of a new Soviet presidium with other socialist parties on the basis of proportional representation in September 1917. Deutscher described Trotsky as the " Soviet's moving spirit " in 1905 and highlighted his representation of Bolsheviks, Mensheviks and the rest of the Soviets on major occasions. Rogovin stated that the Left Opposition, led by Trotsky, was a political movement that "offered a real alternative to Stalinism, and that to crush this movement was the primary function of the Stalinist terror ". He also attributed the eventual formation of a one-party system to the conditions which were "imposed on Bolshevism by hostile political forces".

Conversely, other figures such as Volkogonov have strongly criticised his defence of the Red Terror and dictatorship of the proletariat. Service argued that his "ideas and practices laid several foundation stones for the erection of the Stalinist political, economic, social and even cultural edifice". Cherniaev considered Trotsky to be partly responsible for the establishment of a one-party, authoritarian state and initiating several military practices such as summary executions which later became standard practice during the Stalinist era. Thatcher cited his defence of terror in his work, Terrorism and Communism: A Reply to Karl Kautsky, but also acknowledged that Trotsky was capable of leniency and had personally urged that White army deserters be treated with understanding.

This view has been disputed by some writers such as French socialist historian Pierre Broue who criticised Western representations of Trotsky's role in the Kronstadt rebellion which he argued had falsely presented Trotsky as the principal figure that led and was responsible for the repression. He also added that military tribunals and executions for desertions were a common feature of every war and not exclusive to the actions of the Red Army under Trotsky. Dukes believed Trotsky had been maligned and caricatured as a historical figure which necessitated a historical reappraisal. Patenaude regarded Service's characterisation of Trotsky as a "mass murderer and a terrorist" to be reflective of a wider attempt to discredit Trotsky as a historical figure and noted his work featured several inaccuracies and distortions of the historical record. Daniels argued that many of the distinctive features of Stalin's rule such as his campaigns against " bourgeois experts " as seen with "the Shakhty trials, his contemptuous anti-intellectualism and the dogmatization of Marxism, the purges —run totally counter to Trotsky's thought".

Various historians have credited Trotsky and the Left Opposition with shifting the Soviet economic orientation from the NEP policy towards a planned economy through their proposals for mass industrialization. Trotsky had delivered a joint report to the April Plenum of the Central Committee in 1926 which proposed a program for national industrialization and the replacement of annual plans with five-year plans. His proposals were rejected by the Central Committee majority which was controlled by the troika and derided by Stalin at the time. The eventual adoption of the five year plans in 1928 would serve as the basis for Soviet modernization. On the whole, historian Mark Sandle characterised his vision for socialist construction as “more industrialist, modernist, centralising and technocratic” than the economic proposals presented by rival theoretician Bukharin.

Several scholars have regarded his historical writings on the Soviet bureaucracy as having a considerable influence in shaping the receptive attitudes of later Marxists and many non-Marxists. Trotsky associated bureaucratism with authoritarianism, excessive centralism and conservatism. Political scientist Baruch Knei-Paz argued that Trotsky had done more than any other political figure to "show the historical and social roots of Stalinism" as a bureaucratic system. British cybernetician Stafford Beer who worked on a decentralized form of economic planning, Project Cybersyn from 1970 to 1973, was reported to have read and been influenced by Trotsky's critique of the Soviet bureaucracy. Other historians have noted the literary value of his account of historical events and social analysis with works such as 1905 and The History of the Russian Revolution for wider historiography.