Key PointsMykhailo Fedorov was appointed Ukraine's defence minister at the start of the year.Fedorov's push to modernise the military was rumoured to have caused friction with parts of the establishment.When 35-year-old Mykhailo Fedorov was appointed Ukraine's defence minister, he was the youngest ever to hold the position. Just six months later, his removal has sparked protests across Ukraine.The former tech entrepreneur's departure came amid a surprise government reshuffle announced by Ukrainian President Volodymyr Zelenskyy this week that also included the dismissal of Prime Minister Yulia Svyrydenko.Fedorov's removal was viewed as the result of infighting inside Ukraine's military establishment between Fedorov and Oleksandr Syrsky, commander-in-chief of Ukraine's armed forces. Federov oversaw the defence ministry during a period in which Ukraine reversed some of Russia's battlefield momentum.He said he had declined an offer from Zelenskyy to serve as an adviser after the president refused to include him in the next government.News that makes senseYour trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.Yevgeniy Khmara, head of Ukraine's SBU security service, has been appointed acting defence minister.Who is Mykhailo Fedorov?Fedorov had a reputation as a young, innovative moderniser who sought to reform the Ukrainian military. He has championed the use of advanced technology to fend off Russian attacks, becoming the public face of the country's popular drone program.Before becoming defence minister, he served as Ukraine's minister of digital transformation and a close technology adviser to Zelenskyy. He was the last remaining minister to have held positions in all of Zelenskyy's governments, having stayed close to the president since his election in 2019.His supporters credited him with helping to slow Russia's advances this year, in part through his push to ramp up long-range drone strikes, cut bureaucracy, and use a data-driven approach to the war effort.Protesters turned out in multiple Ukrainian cities over the decision to replace Federov. Source: Getty / Global Images UkraineHe also boosted military salaries and, before becoming defence minister, introduced computer game-like reward systems that allowed drone teams to earn rewards for striking Russian targets.Earlier this year, Fedorov, who has close ties to Silicon Valley executives, negotiated an agreement with billionaire Elon Musk that saw Russia lose access to the Starlink satellite internet service on the battlefield.Ukraine made its largest territorial gains in years following the agreement. Why was Fedorov replaced?Fedorov's push to modernise the military was rumoured to have caused friction with parts of the establishment.Speaking to reporters following the reshuffle this week, both Fedorov and Zelenskyy effectively confirmed those suspicions. Fedorov said he had a dispute with Syrsky, accusing the army chief of blocking the defence ministry's initiatives and dividing the country.He criticised slow bureaucracy and a lack of flexibility, questioning whether Ukraine could defeat Russia with Syrsky in charge of the army.Speaking from Kyiv, Zelenskyy said he expected the defence ministry and military leaders to work with greater unity, acknowledging there had been "systemic" conflicts between them."A president in wartime should not have to choose in such a situation, honestly," he said, accompanied by UK Prime Minister Keir Starmer."I would very much like unity."In a message on Telegram, Syrsky said he would continue to "focus on the war" and wished Fedorov "continued success".Why were people protesting?Thousands of protesters demonstrated in Kyiv and other Ukrainian cities after Federov's dismissal, carrying signs and singing the Ukrainian national anthem. "We saw results from his tenure, when strikes were effectively carried out against targets in Russia," protester Viktoriia Osypenko, 24, told the Agence France-Presse news agency.Vlada Roman, a 30-year-old business owner, said the "dismissal is a slap in the face of the Ukrainian people", accusing Zelenskyy of being "afraid of effective people". Thousands of protesters took to the streets of Kyiv, calling on Ukraine's president to reinstate the defence minister. Source: Getty / Global Images UkraineShe said she hoped the president would reverse the decision after the demonstrations.The deputy commander of Ukraine's air force, Pavlo Yelizarov, also resigned in solidarity."It is a great honour for me to work with Mykhailo Fedorov. In 2022, I joined the defence forces to win, not to pretend to be doing something," he said in his resignation statement.Sergii Koretskyi has been confirmed by the Ukrainian parliament as the country's new prime minister— With additional reporting by Reuters and Agence France-Presse.For the latest from SBS News, download our app and subscribe to our newsletter.