President Volodymyr Zelensky’s move to replace his defense minister, Mykhailo Fedorov, prompted street protests in cities across Ukraine on Thursday.

Mr. Fedorov had become the youthful face of his country’s successful drone warfare program. But, as part of a broader government reshuffle, Mr. Zelensky has chosen not to nominate him to return to the post of defense minister.

Lawmakers were expected to vote on Mr. Zelensky’s new cabinet later on Thursday — and many protesters were urging them to resist the move to replace Mr. Fedorov.

How long was he in his post?

Mr. Fedorov became Ukraine’s youngest-ever defense minister when he was appointed just six months ago. His appointment was seen as an endorsement by Mr. Zelensky of Mr. Federov’s tech-driven vision.

How did that go?

Ukraine has been experiencing a surge of optimism in recent weeks — one which Mr. Fedorov had helped to create. His tenure coincided with successful long-range drone strike campaigns that have hit refineries and other sites in Russia, as well as in the Crimean Peninsula.

Mr. Fedorov had maintained ties with Silicon Valley executives interested in the transformation of warfare on Ukraine’s battlefields. He met repeatedly with Alex Karp, the chief executive of the data and analytics company Palantir, and he took credit this year for persuading Elon Musk to shut off Russia’s access to the Starlink satellite internet service, blinding Russian drones for a time.

But during his tenure, Mr. Fedorov clashed with seasoned military generals who saw aspects of his robot war vision as fanciful and who argued for the continued need for infantry deployments.

Mr. Fedorov also angered established defense contractors with programs threatening their businesses, such as one that allowed soldiers to buy their own weapons on the website Brave1 Market, nicknamed the “Amazon of Weapons.”

What was his background?

Mr. Fedorov had previously led a ministry focused on e-government initiatives and for years had been Mr. Zelensky’s closest adviser on technology.

Even before leading the Defense Ministry, Mr. Fedorov had championed military innovations. He gamified war for drone teams by awarding points for blowing up tanks, howitzers or enemy infantry, a program that was popular in the army.

How will his departure affect the war?

Mr. Fedorov had long been Ukraine’s most prominent proponent of fighting with drones and robots, and his ouster raises questions about the future of Ukraine’s innovation-centered strategy for confronting the much larger Russian Army.

In a social media post on Wednesday confirming his departure, Mr. Fedorov described his approach to war as fighting with the “speed of innovation.”