Odesa, grain port to the world, city of creative mingling, scarred metropolis steeped in Jewish history, is the big prize in the war and a personal obsession for Mr. Putin. In a speech three days before ordering the Russian invasion, Mr. Putin singled out Odesa with particular venom, making clear his intention to capture “criminals” there and “bring them to justice.”

Mr. Putin believed at the outset of the war that he could decapitate the Ukrainian government and take Kyiv, only to discover that Ukraine was a nation ready to fight for the nationhood he dismissed. As the focus of the fighting shifts to southern Ukraine, Mr. Putin knows that on Odesa’s fate hinges Ukrainian access to the sea and, to some degree, the world’s access to food. Without this city, Ukraine shrivels to a landlocked rump state.

“Odesa is the key, in my view,” said François Delattre, the secretary general of the French Foreign Ministry. “Militarily, it is the highest-value target. If you control it, you control the Black Sea.”…

Almost six months into the war, Odesa resists, not untouched, but unbowed. On its broad tree-lined avenues, redolent of linden blossom, where stray cats slither and a golden light bathes the gray-green, ocher and light blue buildings, a semblance of everyday life has returned. Restaurants and the storied Opera Theater, founded in 1810, have reopened. People sip coffee on the elegant Derybasivska Street. Insouciance is one expression of Odesan pride.

But an insidious unease lurks beneath it. The war is close, its front line no more than 80 miles to the east. Sandbags filled from deserted city beaches and anti-tank “hedgehog” obstacles of angled metal bars form barricades on many city blocks. Night patrols enforce an 11 p.m. curfew.