“Those who come to Europe now are not refugees,” Mr. Nizamov said, dressed in a long-sleeve T-shirt with the image of King Simeon the Great, who ruled Bulgaria during the late ninth and early 10th centuries. Their goal, he said, is “to spread Islam” across Europe.

The groups remain relatively small, as focused on stirring up political support and media attention as on confronting migrants, and not all of them are actively patrolling. In Hungary, Mr. Vass posted a call last year to the Hunyadi Border-Guard Unit “to be prepared to step up for your own defense.” But the authorities later dropped an investigation after it became clear that the group had done nothing but prepare to take action.

Not only are there few migrants coming through Slovakia at the moment, but the government, like those of most countries in the region, is strongly resisting pressure from Western Europe to accept asylum seekers for resettlement.

Nonetheless, People’s Party-Our Slovakia, led by Marian Kotleba, is patrolling trains, so far without having to save anyone from a migrant attack. And Vzdor Kysuce is organizing and training paramilitary groups that it says would patrol the streets if migrants ever did appear in Slovakia. Mr. Magat, the party’s leader, calls the 20 people who have signed up as paramilitaries “sleeping soldiers” who have been trained to “protect the white majority” just as “people in Germany took their guns and started solving problems themselves in 1930s.”