Liberation of Ohrdruf — United States Holocaust Memorial Museum

On April 4, 1945, US forces liberated the Nazi death camp Ohrdruf in Germany. From the article:

Liberation of Ohrdruf — United States Holocaust Memorial Museum
Liberation of Ohrdruf
Annotated album page documenting the liberation of Ohrdruf concentration camp, a subcamp of Buchenwald (mislabeled as Dachau) from the album of Henry Raymond Malenfant, 4th Armored Div, 84th Reconnaissance Battalion.
Annotated album page documenting the liberation of Ohrdruf concentration camp, a subcamp of Buchenwald (mislabeled as Dachau) from the album of Henry Raymond Malenfant, 4th Armored Div, 84th Reconnaissance Battalion. —US Holocaust Memorial Museum, courtesy of Raymond Malenfant
April 4, 1945
The Ohrdruf camp was a subcamp of the Buchenwald concentration camp, and the first Nazi camp liberated by US troops.

The 4th Armored Division and the 89th Infantry of the Third US Army liberated Ohrdruf on April 4, 1945. After visiting Ohrdruf a week later, General Dwight D. Eisenhower ordered careful documentation of the atrocities perpetrated in the Nazi concentration camps, so that no one in the future could deny that they had committed these atrocities. The discovery of the Ohrdruf camp opened the eyes of many US soldiers to the horrors perpetrated by the Nazis during the Holocaust.

US soldiers confront the corpses of prisoners killed in Ohrdruf shortly before the camp’s liberation. Ohrdruf, Germany, April 4, 1945.
US soldiers confront the corpses of prisoners killed in Ohrdruf shortly before the camp's liberation. Ohrdruf, Germany, April 4, 1945. —US Holocaust Memorial Museum, courtesy of Roy Rodriguez, 10th Armored Infantry Battalion of the 4th Armored Division
Page 1 of Letter from US Soldier Aaron Eiferman
Page 1 (of 5) of a letter from US soldier Aaron A. Eiferman to his wife.
Page 1 (of 5) of a letter from US soldier Aaron A. Eiferman to his wife. Read the full letter
Transcript
April 27, 1945
US soldier Aaron A. Eiferman, with the 12th Armored Division, writes a letter to his wife describing conditions in Kaufering IV, one of the Nazi concentration camps in the Landsberg area.

As Allied troops moved across Europe in a series of offensives against Nazi Germany, they began to encounter tens of thousands of concentration camp prisoners. Throughout the spring of 1945, American and Allied forces liberated numerous concentration camps as they closed in on Berlin. The battle-hardened Allied soldiers were shocked at what they discovered. As Eiferman wrote,

We have seen what can be called the living dead

Some five months after the D-Day invasion of western Europe, the 12th Armored Division entered France through the port of Le Havre and quickly made its way eastward toward Alsace by early December. In March 1945, the “Hellcats” advanced into the Rhineland and captured the city of Ludwigshafen on March 21. Deploying southward, the unit took the city of Würzburg early the next month. By the end of April, the 12th had advanced well into Bavaria and had reached the Danube River. The division ended the war in Austria.

During its penetration of southern Germany, the 12th overran this Dachau subcamp in the Landsberg area on April 27, 1945."