“We are a little bit shocked,” the captain said. “We worked next to each other, we studied together.” It was barely credible that such closeness could fall apart in the space of a week, he said.

That feeling was widespread in Sevastopol and the surrounding region, as what largely seemed like a phantom war fueled both dread and disbelief.

One woman who had no doubt that the appearance of mysterious armed forces in her town was nothing but bad news was Elmira Ablyalimova, 39, who confronted camouflage-clad soldiers surrounding the Ukrainian military base in her hometown Bakhchysaray.

She sought out their commander after a cluster of his soldiers, their guns draped over flak jackets or propped against trees, drank water just a few feet away from local children playing in a primitive playground on the edge of the small base.

“Please, I am begging you,” she beseeched the commander, a silent man who had descended from a military transport truck. “You’re a handsome young man, you must have a wife and children and parents, a family of your own. We don’t need you here in our town to protect us.”

He listened for several minutes then moved away, she said. Ms. Ablyalimova, who said she worked in the local administrative government, was furious. “We all know each other here” in the town of 27,000, she said.

Self-defense forces who were also patrolling outside the small base — from which the blue and yellow Ukrainian flag still waved — consisted mostly of men from different towns, she said. “I never saw them before — and they are the ones who think this is good,” Ms. Ablyalimova said.