Immigration and Customs Enforcement’s Homeland Security Investigations worked with Brazilian authorities to stop neo-Nazis from planning and executing a mass-casualty attack on New Year’s Eve in São Paulo. According to Brazil’s Ministry of Justice and Public Security, four arrest warrants and 31 search-and-seizure warrants were executed Thursday in the states of Rio de Janeiro, São Paulo, Minas Gerais, Rio Grande do Norte, Paraná, Santa Catarina and Rio Grande do Sul as part of Operation Bergon, which targeted antisemites and neo-Nazis networking online and threatening acts of violence. The operation, which was launched in May in response to neo-Nazi groups using...