In Bulgaria, in 1934, on a muddy street in the river town of Vidin, Khristo Stoianev saw his brother kicked to death by fascist militia.

His brother was fifteen, no more than a blameless fool with a big mouth, and in calmer days his foolishness would have been accommodated in the usual ways—a slap in the face for humiliation, a few cold words to chill the blood, and a kick in the backside to send him on his way. That much was tradition. But these were political times, and it was very important to think before you spoke. Nikko Stoianev spoke without thinking, and so he died.

On both sides of the river—Romania to the north and Bulgaria to the south—the political passion ran white hot. People talked of little else: in the marketplace, in the church, even—a mark of just how far matters had progressed—in the kitchen. Something has happened in Bucharest. Something has happened in Sofia.

Soon, something will happen here.

And, lately, they marched.

Torchlight parades with singing and stiff-armed salutes. And the most splendid uniforms. The Romanians, who considered themselves much the more stylish and urbane, wore green shirts and red armbands with blue swastikas on a yellow field. They thrust their banners into the air in time with the drum: we are the Guard of Archangel Michael. See our insignia—the blazing crucifix and pistol.

They were pious on behalf of both symbols. In 1933, one of their number had murdered Ion Duca, the prime minister, as he waited for a train at Sinaia railway station. A splinter group, led by a Romanian of Polish descent named Cornelius Codreanu, called itself the Iron Guard. Not to be outdone by his rivals, Codreanu had rec...