“We have given up on Baghdad now that the Iraq we fought for is broken,” said Hoshyar Zebari, Iraq’s former foreign minister and a leader of the referendum effort. Mr. Zebari said the Shiite Muslim-led Baghdad government had aligned with Iran, no friend of Iraq’s Kurds or the United States.

The Kurds’ generations-long sense of mistrust and insecurity is playing out in the political showdown with the United States, which fears the referendum will foment ethnic violence, fracture Iraq and rupture the coalition against the Islamic State.

“The Kurdish psyche is one of being different — and very bitter over how the rest of the world looks at us, especially the Arabs,” said Alan Noory, a Kurdish university professor.

Mahdi Ahmed Hamza, 49, a school headmaster, said he had always felt like a second-class citizen, barely tolerated by Iraqi Arabs outside Kurdistan.

“It’s like you are a bird in a cage that has food brought to it,” Mr. Hamza said. “But only when you are able to fly away do you discover that you are able to feed yourself.”

For Lt. Esra Salim, a pesh merga soldier, the sound of knocking will be playing in her head when she votes “yes” on Monday. She said she would always remember Iraqi security forces constantly knocking on her family’s door, searching for male relatives hiding in attics and garden sheds. Many Kurdish men were killed, imprisoned or pressed into military service.

Lieutenant Salim, 26, said her family was forcibly evicted and replaced by Arabs in the 1980s.

“We can never, ever let that happen again,” she said. “This is why I fight — and why I will vote for independence.”