As soon as Hitler's armies were pushed back into Germany, the Red Army and the NKVD began to comb the captured territories. By 23 May they reported arrests of 268 former Red Army men, 1,208 men, and 1,655 civilians. In the following weeks the British surrendered over 40,000 Cossacks who had fled to Western Austria from Soviet authorities and certain death. In July and August, the Soviets brought in four regiments of NKVD troops to "mop up" Vienna and seal the Czechoslovak border.