Mikhail Markovich Gruzenberg, known by the alias Borodin (9 July 1884 – 29 May 1951), was a Bolshevik revolutionary and Communist International (Comintern) agent. He was an advisor to Sun Yat-sen and the Kuomintang (KMT) in China during the 1920s.

Born in a rural part of the Russian Empire (now Belarus), to a Jewish family, Borodin joined the General Jewish Labour Bund at age sixteen, and then the Bolsheviks in 1903. After being arrested for participating in revolutionary activities, Borodin fled to America, attended Valparaiso University, started a family, and later established an English school for Russian Jewish immigrants in Chicago. Upon the success of the October Revolution in 1917, Borodin returned to Russia, and served in various capacities in the new Soviet government. From 1919, he served as an agent of the Comintern, travelling to various countries to spread the Bolshevik revolutionary cause. In 1923, Joseph Stalin picked Borodin to lead a mission to China, where he was tasked with aiding Sun Yat-sen and his Kuomintang. Following Sun's death, Borodin assisted in the planning of the Northern Expedition, and later became an integral backer of the KMT leftist government in Wuhan.

Following a purge of communists from the Kuomintang, Borodin was forced to return to the Soviet Union in 1927, where he would remain for the rest of his life. He once again served in various positions within the Soviet government, and later helped found The Moscow News English-language newspaper, of which he would become the editor-in-chief. During the Second World War, he additionally served as editor-in-chief of the Soviet Information Bureau. Amidst rising antisemitism in the Soviet Union during the late 1940s, Borodin was arrested and deported to a prison camp. He died in 1951 and was officially rehabilitated in 1964.

Early life Borodin was born Mikhail Markovich Gruzenberg () to a Jewish family in Yanovichi, Russian Empire, now part of Vitebsk Region, Belarus, on 9 July 1884. At a very young age, he began work as a boatman on the Western Dvina, traversing the stretch of the river between Vitebsk, Dvinsk, and Riga, now the capital of Latvia. He later moved to Riga, where he attended Russian-language night schools while working in the city's port. He joined the General Jewish Labour Bund at age sixteen, switching allegiance to Vladimir Lenin's Bolsheviks in 1903. He became a close associate of Lenin, making use of his knowledge of the Yiddish, German, and Latvian languages in work as a Bolshevik agent in the empire's northwest region. In mid-1904, he was ordered to travel to Switzerland to meet Lenin, who had gone into exile. Following the "Bloody Sunday" massacre of unarmed protesters by Tsarist troops in Saint Petersburg on 9 January 1905, Borodin returned to Russia, organised revolutionary activity in Riga, and was later selected to attend the Bolshevik conference at Tampere, where he met Joseph Stalin.

In 1906, he attended the 4th Congress of the Russian Social Democratic Labour Party in Stockholm. Later that year, he was picked up by the Tsarist police in Saint Petersburg, and given the choice of either being sent to Siberia or exile in Europe. Borodin chose exile, and by October, he had arrived in London, where police took notice of his activities and promptly ordered him out of the country. In 1907, he arrived in America, first to Boston, and then on to Chicago. While there, he attended classes at Valparaiso University in Indiana, taught English to immigrant children at Jane Addams' Hull House, and then opened his own school for Russian Jewish immigrants, which later grew into a successful business venture. During his time in the United States, Borodin associated nominally with the Socialist Party of America, whilst simultaneously promoting the Russian revolutionary cause in the immigrant community.

After the October Revolution Following the October Revolution of 1917, he returned to Russia in July 1918, and began working in the People's Commissariat for Foreign Affairs of the Russian Soviet Republic. Some months later, he returned to America to relay Lenin's "Letter to American Workers", a propaganda message intended to counteract negative views of the Russian communists following the signing of the Treaty of Brest-Litovsk. He also proposed a joint propaganda campaign with George Creel's Committee on Public Information, though this never came to fruition. Having become disillusioned by the intensity of American criticism of the new Soviet government, Borodin gave up hope of co-operation with the Americans, and returned to Russia. He then moved on to Stockholm, where he visited American writer Carl Sandburg, with whom he discussed the Bolshevik revolution.

In March 1919, Borodin participated in the first congress of the Communist International (Comintern) in Moscow. After the congress, he embarked on his first Comintern assignment, travelling with a falsified Mexican diplomatic passport. Borodin travelled through a variety of European countries, deposited Soviet funds in a Swiss bank account, and otherwise tried to raise money to finance the establishment of communist parties in the Americas. He then travelled to Santo Domingo, from which he booked passage to New York, where he arrived in August 1919. His mission was known to the American authorities, and as such he was briefly detained by the Bureau of Investigation upon arrival. After his release, he went on to his former home, Chicago, where the Socialist Party of America was embroiled in a dispute between its left wing, who wanted to establish a communist party and join the Comintern, and the "regulars", who were opposed. Borodin, conscious of the fact that his activities were being monitored, kept a low profile while in America, and on 4 October 1919, he slipped across the border into Mexico.

In Mexico, he met Indian revolutionary M. N. Roy, the American writers Carleton Beals and Michael Gold, and American communist Charles Phillips. Borodin taught Roy about the Russian Revolution and communism, and it was under Borodin's influence that he took up communist beliefs. Together with the newly emboldened Roy, he helped establish the Mexican Communist Party. During his time in Mexico, Borodin sent reports of Roy's exploits to Lenin, who subsequently invited him to attend the 2nd World Congress of the Comintern in Moscow, which would take place in July–August 1920. Leaving Mexico in December 1919, Borodin, Roy, and Phillips travelled to western Europe, where they intended to spread the communist cause in the lead up to the congress, specifically hoping to establish a communist party in Spain. Arriving in Moscow in the weeks before the congress, Borodin introduced Roy to Lenin, after which he went on to become a major figure in the Comintern.

Borodin later returned to Britain under the alias "George Brown", where he was tasked with ascertaining the cause of the revolution's failure there, and reorganising the British Communist Party. He travelled from city to city in the guise of a trade union representative, successfully avoiding the local authorities until 22 August 1922, when he was arrested in a fifty-man police operation in Glasgow. He was jailed for six months, ostensibly for breaking immigration regulations, though his political mission was known. As Borodin had entered the country without a passport and denied holding Soviet citizenship, the British authorities struggled to process his deportation. His return to Russia was facilitated by a secret Anglo-Soviet agreement; upon completion of his sentence, he was sent back to Russia as a stateless person.

Following his release, Borodin was selected by Joseph Stalin to lead a mission to China. On 2 August 1923, the Soviet politburo issued an order appointing Bordin as its "political advisor" to Sun Yat-sen's revolutionary government, which was then based at Guangzhou in the south of the country. Concurrently, it made Lev Karakhan its chief envoy to the internationally-recognised Beiyang government in Beijing, and ordered the two men to co-ordinate their activities. On his journey to Guangzhou, Borodin stopped at Shenyang in Manchuria to hold talks with the Fengtian clique warlord Zhang Zuolin before proceeding to Beijing, where he met Karakhan. He then sailed for Guangzhou, arriving in the city on 6 October 1923.

The China mission Advisor to Sun Yat-sen (1923–1925) Following Sun Yat-sen's request for help from the Comintern, Borodin was ordered to lead a contingent of Soviet advisors to Guangzhou, where Sun had established a revolutionary government in the aftermath of the Constitutional Protection Movement. Borodin understood no Chinese; English was to be the medium of discussion between the two. Borodin was known for speaking with a clear midwestern American accent that offered no indication of his Russian origin, allowing him to easily communicate with the largely anglophone and American-educated leadership of the Kuomintang (KMT).

Greeted upon his arrival in Guangzhou by Eugene Chen, with whom he later became close, Borodin found that Sun's government was teetering on the brink of collapse. Faced with rampant corruption, anti-Bolshevik feeling in parts of the KMT, and the ever-present threat of the warlords and the Beijing-based Beiyang government, Borodin was tasked with reforming the Kuomintang into a potent revolutionary force. Shortly after his arrival, Borodin identified lack of popular support as the KMT's primary shortcoming, and urged Sun to mobilise the Chinese masses.

Borodin negotiated the First United Front between Sun's KMT and the nascent Chinese Communist Party (CCP), convincing that party, which consisted of only about 300 members at that time, that the alliance was in its long-term interest, as it would facilitate the organisation of both urban and rural workers. Under Borodin's tutelage, both parties were reorganised on the Leninist principle of democratic centralism, and training institutes for mass organisation were established, such as the Peasant Training Institute, where the young Mao Zedong served, and the Whampoa Military Academy, which trained officers for the National Revolutionary Army (NRA) under the leadership of Chiang Kai-shek. He arranged shipments of Soviet arms and shrewdly kept a balance between the middle-class elements of the KMT and the more radical CCP.

When the forces of rebel general Chen Jiongming threatened Sun's base in Guangzhou in November 1923, Borodin proposed a mobilisation of the masses in defence of the city. To accomplish this, he suggested a promise of redistribution of landlord property to the local peasantry, an eight-hour working day for urban labourers, and a minimum wage. Sun rejected land reform because of strong opposition from some of his allies, though agreed to the proposals in principle, and offered a 25% rent reduction instead. In the event, Sun's military forces were able to drive the rebels away, and the rent reduction proposal was never implemented.

In March 1924, negotiations between Soviet envoy Lev Karakhan and the Zhili-clique controlled Beiyang government reached a deadlock, with the Chinese side incensed by Soviet demands to retain control of the Chinese Eastern Railway. Borodin received orders from Moscow to engage in secret talks with Zhang Zuolin, leader of the rival Fengtian clique, whom he had met on his way to Guangzhou. He travelled to Shenyang during April and May 1924, where he negotiated a deal with Zhang. The Soviets would recognise Manchuria's autonomy under Fengtian rule. In exchange, they would be granted joint control of the railway. Upon hearing of this, the Beiyang government dropped its previous opposition. In a deal signed on 31 May 1924, it agreed to grant the Soviets joint control of the railway, and the right to station Red Army troops in Manchuria.