After being caught off guard at Majdanek, the Nazis realized that the Soviets would end up finding every camp within Eastern Europe (with all of the prisoners and guards still present) if something were not to be done. As a result, by mid January, the SS and Nazi-controlled police units had begun forcing thousands of camp prisoners from Poland, East Prussia, Silesia and Pomerania to walk westward away from the advancing Red Army. The death marches, which took place over hundreds of kilometers in sub-zero conditions without food and medicine, resulted in thousands of concentration camp prisoners and allied POWs dying en route. It is estimated that in March and April 1945 at least 250,000 men and women were marched on foot to the heartland of Germany and Austria sometimes for weeks at a time.