On 7 April 1944 a Slovakian Jew, Rudolf Vrba (born Walter Rosenberg), and a fellow prisoner, Alfred Wetzler, succeeded in escaping from Auschwitz-Birkenau. As block registrars both men had been allowed relative (though always risky) freedom of movement in the camp and thus had been able to observe the massive preparations underway at Birkenau of the entire killing machine for the eradication of Europe's last remaining Jewish community, the 800,000...