It is hard to answer with so little context, however during the war, when the allies found out about concentration camps- they did not know the extent of it. Their primary concern was to defeat Hitler's regime to stop the spread of Nazi/ totalitarian sentiments. When they began their invasion into Germany, the allies, especially the soviets, began liberating the camps. What they found horrified them beyond belief. They did not realize the horrendous extent of Hitler's torture. They then realized how horrible those camps truly were.
But like I said, their primary goal during the war was not to liberate the camps. It was to defeat Hitler.
