India, April 17 -- When a Ukrainian agricultural tycoon founded a volunteer unit of 30 people in the early days of Russia's invasion, he had no certainty he would live to see what came next - but he did, and so did the force he created.

The group is now a 40,000-strong corps widely seen as one of Ukraine's most effective fighting formations within official defence forces.

"Ukraine needs to have an effective modern army. And this is our number one guarantee of the country's security," said Vsevolod Kozhemyako, owner of a large agricultural conglomerate and now an adviser to the Commander of the Khartiia Corps.

Its rapid expansion reflects a broader transformation of Ukraine's military, part of a new wave of formations, alongside the Thi...