In a strange twist, President Vladimir V. Putin of Russia is both the man who most wants change stopped and the one who has created the best opportunity for it. The war frightened everyone, including people in Ukraine’s south and east who for decades had been deeply ambivalent about being Ukrainian.

It has also electrified a new generation of activists, who are the moral conscience of the new government, watching what it does from their seats in Parliament and reporting back to the public, like a Greek chorus. (Recent stunts include throwing rotten tomatoes at a board stapled with politicians’ faces.)

So who are Ukraine’s reformers? Many have come from business. Most came of age in the twilight of the Soviet Union. A number of them ran investment funds. There is even a Ukrainian-American, Natalie Jaresko, from Chicago, who moved to Ukraine in the early 1990s to work for the American government. She is now finance minister.

“The type of people coming in are very different from what I’ve seen before in Ukrainian politics,” said Erik Berglof, director of the Institute for Global Affairs at the London School of Economics. “They are young. Many were trained abroad. Most are well off. They are from business and many have run complex organizations.”

Anders Aslund, a senior fellow at the Peterson Institute for International Economics in Washington, pointed out that only two of the new ministers do not speak English, the opposite of the previous government in which only two ministers did speak English.

For Mr. Shymkiv, even the smallest changes have been difficult. Only half of the more than 400 employees of the presidential administration had ever used email (a third had never used a computer), and getting them to overcome their strong affection for the fax machine has been hard. A person of the wired world, Mr. Shymkiv is using a Windows smartphone in an office where giant Soviet telephones sit like bricks on his desk.

One immediate problem is cash. The country is running on fumes in terms of hard currency reserves, in part a result of a large payment recently to Russia for its gas debt. Without a substantial cash infusion from the International Monetary Fund, the country is likely to suffer an economic meltdown, with far-reaching consequences for its currency, banking system and its new government’s reputation. Russia’s wobbly finances do not help — about a quarter of Ukraine’s exports go to Russia.