As "Einsatzgruppe" A advanced into Lithuania, it actively recruited local nationalists and antisemitic groups. In July 1941, local collaborators, pejoratively called "White Armbands" (), joined the massacres. A pogrom in Riga in early July killed 400 Jews. Latvian nationalist Viktors Arājs and his supporters undertook a campaign of arson against synagogues. On 2 July, "Einsatzgruppe" A commander Stahlecker appointed Arājs to head the "Arajs Kommando", a "Sonderkommando" of about 300 men, mostly university students. Together, "Einsatzgruppe" A and the "Arājs Kommando" killed 2,300 Jews in Riga on 6–7 July. Within six months, Arājs and his men would kill about half of Latvia's Jewish population.