Mr. Hubbard, a 74-year-old teacher, was held for more than four years on what the State Department called fabricated charges.

© Moscow City Court Press Service

The move buys good will with President Trump while costing the President Vladimir V. Putin — who is wanted for war crimes — little.

© Moscow City Court, via Associated Press

Stephen Hubbard was a wanderer. But when he moved to Ukraine, the war brought arrest, torture and imprisonment. He turns 73 this week.

Where the two presidents’ war of words will end is anybody’s guess. But if it continues, it could threaten the crucial operational help that Ukraine still gets from the United States.

© Tierney L. Cross/The New York Times

A day in the Ukrainian capital, a new kind of battlefield far from the front, where daily life means assessing — and accepting — deadly risks.