In the weeks after President Vladimir V. Putin of Russia ordered the invasion of Ukraine, Kyiv, the capital, became a city transformed. Much of its population evacuated. New defense units gathered and took up arms. Impromptu social support — field kitchens, aid stations, bomb shelters, evacuation convoys — sprouted into functional shapes. The city endured intermittent bombardment throughout. This altered streetscape became the uneasy milieu of Alexander Chekmenev, a Ukrainian documentary and portrait photographer who since the 1990s has visually chronicled his country’s post-Soviet life. Like many of his fellow citizens, Chekmenev, who is 52, took care of his family early on, ensuring that his teenage daughter reached safety in Slovakia. He himself opted to remain. In a climate of indiscriminate attacks, a circumstance in which anyone might be randomly harmed at any time, he felt an imperative to work, venturing out on assignment for The New York Times Magazine to find those who stayed put.